A/N: Based on episode 53: Mr Butt. This is quite interesting.
Robin went over to Starfire's door and knocked. When it opened it, Starfire opened it and smiled.
"Hey Star." He greeted.
"Hello Boyfriend Robin." She greeted back as he entered her room, closing and locking the door. Without wasting any time, the titan leader went to his girlfriend instantly and captured her in his arms, kissing her and, with each hand, groped one of her breasts and butt cheeks. She squeaked from surprise but nonetheless joyfully accepted his sudden advance as they backed to her bed and fell down onto it. They moaned as they played with each other passionately while kissing with all the warmth and love they could muster. That is until a shadow of a volumptuous female floated down from outside of Starfire's window, and took them a few seconds to notice. Looking outside, the female titan gasped.
"Blackfire?!" Said darkly dressed sister was grinning in amusement at what she was seeing.
"So, you're my sister's boyfriend." Blackfire was in Starfire's bedroom as she stood above the two sitting titans.
"Sister, what are you doing here? I thought-"
"That I was locked away somewhere? On the run? Nah, I wanted to check how my baby sister was doing, when I caught you doing some...not so baby cute things." She giggled.
"Well, if you must know, we are the together. We love each other." Starfire explained herself.
"Really?" Blackfire raised her eyebrow.
"Yes. I treat her the best I can and make sure she's happy."
"Oh, that part I'm sure of. You two are pretty much two goody two shoes that are a match made in heaven. What I'm actually curious about is if you're worthy." The fair skinned Tamaranean stated.
"Worthy?" The Boy Wonder asked.
"You know, fucking my sister." Both of the teenagers blushed a much deeper red as Starfire stood up with great embarrassment.
"What you think does not matter! I love Robin, and we do not need to prove anything to you Blackfire! You know, I remember when you would take my toys on Tamaran, but I will not let you come in between me and my boyfriend!"
"Oh please, who's to say that he loves you for you? Even though I said what I said about you goody two shoes, what if I'm wrong and that he's only in love with one thing about you?" To nonverbally show what she meant, Blackfire smugly walked forward and shoved her chest into her sister's own, the pair of breasts squishing against each other. "Our grabnacks may not be erotic areas for the Tamaranean female, but I certainly know men loves a good big pair. Not to mention, mine are just slightly larger and more firm. Perhaps he'd enjoy having my body instead."
"Oh no he would not!" Starfire protested, pushing her forehead into Blackfire's along with their busts pushing even closet together. "He prefers the soft and springy kind!"
"You mean sloppy and saggy?" As the two sisters growled at each other, Robin just couldn't remain quite anymore.
"Don't I get a say in this?" The Tamaranean girls turned towards him, one arrogant with a grin and the other that instantly gone from angry to desperately hopeful.
"Nope. You're in luck, Boy Wonder. You're going to be the judge on which of us is better and is truly deserving. And of course that's going to be me."
"Boyfriend Robin, please keep me. If I have your wording right, I will not lose to my 'tramp' of a sister." The titan leader gulped from hearing this. Something told him he couldn't say no to two Tamaranean girls with a rivalry in between each other. Blackfire went first, like she always does, and pushed Robin down onto the bed and started kissing him while taking his hands to guide them to her breasts, which indeed feel firmer. While Starfire's felt like jelly, Blackfire was like the density of cold pudding. Still his fingers sunk into her boob flesh. Feeling her nipples start to become hard, he decided to pinch and pull them, making the alien girl groan.
"Oh yeah, I like that, but I want more." The fair skinned Tamaranean said as she then guided one his his hands to below her skirt, his hand now on her clothed haringor. Realizing where this was heading, the Boy Wonder used all the strength he could to tip Blackfire over, and get above. "Oh, so you want to lead at this part? Hehe, alright, I'll allow it." Robin proceeded to take his clothes off, but she wasn't going to wait that long. "Here, let me help you." She then proceed to rip both his, much to his protest, and her own clothes off to speed up the process. "There, now you can begin." Annoyed she didn't wait, but not wanting to make her annoyed as well, he proceeded to pleasure her by bringing his mouth to lick her pussy while massaging her grebnacks. "Ah, of right there Robin! Yes!" As Blackfire made gratifying noises, Starfire sat in a corner alone and sad as she played with herself, waiting for her turn.
"Robin." The female titan whispered to herself. This went on for some time with Robin licking Blackfire's pussy while she made luscious noises while Starfire silently kept herself occupied messing with her boobs and pussy. But something had to give, and it was the quickness of a Tamaranean female as Blackfire sprayed Robin's face like a broken faucet as she climaxed and screamed. It was weird. Starfire tasted bitter while Blackfire was sweet. Was this the only regard where the practically opposite sisters were also the opposite in one exact regard?
"Ahhhh, well...it seems like...you at least know...how to pleasure a...Tamaranean. Now let's see if you can do so with that dick of yours? Though I doubt it, you're not the biggest I've taken." She tried to put down, but he was determined now. Flipping Blackfire over, he shoved his dick into her pussy, driving her wild. "Ah! This is a bit more than I'd thought it be!"
("This feels surprisingly tight and good. I'm sorry Starfire. At least I'll always choose you.") As he pumped into her pussy, he reached forward to take a grip of her flopping tits, and pinched her nipples.
"Oh yes! I can feel you go all the way! Try to go deeper if you can!" As Blackfire screamed again in climax, going in and out in rapid succession thanks to her biology, Starfire was also reaching her limit. Her chair was wet with her fluids. She thought to herself,
("Ooooh, that looks so good. Why can it not be me being the screwed? I-I cannot be pleased by myself anymore. I want some. I want some of Dick's dick.") Robin let go of Blackfire's breasts so that he gripped her hips to ram into her haringor with even more force. Eventually, both sisters shouted at the top of their lungs as they finally climaxed in unison, including Robin as he squirted his juices into Blackfire. A few minutes later, Blackfire was laying on the ground in her own sweat, recovering from such an experience. Now it was Starfire's turn.
"Robin, please. I need you." The fellow titan cried out, literally crying.
"Don't worry. This time, I'll put love in it. You're the only one I need." He whispered into her ear.
"Robin." She sighed with a smile before they both kissed. Like before, but this time with his own volition, he started massaging her grebnacks before moving his hands below her top and doing so directly. Starfire then realized something then broke the kiss. "Robin, let me show you how much I love you with my body."
"Okay." He nodded. Robin is the one this time to be below, as his girlfriend took off her top and covered his dick with her breasts.
"I bet you love my chest than Blackfire's, right? How do they feel after pounding my sister like that with your dick?"
"They feel...so good Star. My penis is so sensitive, but they feel so soft."
"Like the marshmallows, right? Do not worry. I will treat you with the care that you deserve."
"Boring." Another girls' voice objected, as Blackfire tried to but in and tried to take over the boob job but Starfire was able to keep her share, and the two were at it again over his dick. "Who wants wimpy pampering? The real fun is in doing it rough and strong. Like this!" With a lot of her strength, she mushed her tits together with enough power to actually make it hurt for Robin as he breathed in quickly. Even between a pair of tits it was like his dick was being strangled from the left side!
"Sister, he is just a human! He needs the care and gentleness of one, even if Robin is tougher than most." Starfire protested as she tried to take over, trying to relieve his pain with her delicate approach.
"If he can't even take a boob job of a Tamaranean, than he doesn't deserve someone of you at least."
"You are just the worst, Blackfire."
"I try." The darker, fair skinned sister chuckled with smugness. "No matter how much you protest, what's the point of having a sexual relationship if he can't take it rough?"
"Not everyone wants it rough!"
"Those are just boring people."
"G-girls, I'm going to-ack!" The Titan leader gripped his sheets as he exploded all over the faces and boobs of the Tamaranean sisters, gasping and laughing from the dick they weren't even fully paying attention to. Blackfire was the first to lick at his dick to clean it, with Starfire following, both once again combining a strong and soft approach. Once he was all clean however, Blackfire was not impressed.
"What, broken already? You've lasted longer than most men I've done this with, but how sad, you still fall under my expectation of longevity."
"Blackfire, how much more to you plan on torturing him for this game of yours?! You do not need to push him so far!" Starfire called her out.
"I suppose you're right. Anymore and he may become useless as a human too." Getting tired of their arguing, even if he appreciates Starfire defending him, the Boy Wonder had to take the upperhand. Moving his hands, he managed to find the special G-spot of the Tamaranean girls, and pinched them hard, sending the sisters into cloud 9 in an instant.
"Ah, Robin! That is too hard!" She squealed as her eyes rolled back.
"No-no fair! Using our weaknesses...while we're talking!" Blackfire growled. When Robin put a twist to his pinching, he sent the two into another wave of climaxing, soaking his hands as a result of messing with their genitals. Both fell off the bed as the two girls tried to get over their afterglow. With great struggle, the Titan leader crawled towards his belt which hung partially off Starfire's bed, and got a pellet from one of the compartments. It was too be used as a last resort, if he ever needed a strength and energy boost in a life or death fight. But given that he's a target of affection of two alien girls with more strength and endurance who won't let him stop to rest properly, this seemed appropriate for a dose. Crunching the drug between his teeth before swallowing, he could feel the effects kicking in already. Standing up over the two girls, they saw the titan leader sport a face which showed determination and no nonsense, like he was finally going to take charge.
"Now then, I finally have the opportunity to show both you girls what happens if you just treat a man like a toy, and he just regained his strength thanks to a stimulant while you're worn down." His adrenaline enhanced body was only going to last three minutes, but that's all he needed. Picking up Blackfire effortlessly like she was a person sized doll, and then literally just dropped the fair skinned Tamaranean pussy first onto his dick while making sure he was quick enough to grip her nipples, letting gravity take over as he tugged her up and down by her nipples.
"Huh? Huh?!" She asked first, literally unable to process of what's happening for a few seconds before screaming like a horror movie girl being killed as all the sheer stimulation caught her off guard all at once. "AHHHHHHHH!" No words, just unrestrained shouting with how extreme this felt until he came into her, and then placed her down once his climax ended. Looking over to Starfire like Black was just the first problem on a homework paper, he then went behind his girlfriend and gripped her breasts with such strength, digging his forefingers into her nipples.
"Ah! My nipples! You are pushing them in so forcibly!" She whimpered loudly. Robin smiled that he doing this to his girlfriend as well, but that was nothing as he rammed into her haringor, and pumped in back and forth swiftly, making her cry out with each thrust. "Ah! Ah! Ah! So deep! So strong! What did you take?!" The female titan questioned before climaxing her self, Robin's legs becoming drenched with her fluids. The Boy Wonder felt a hand grip his ankle, and he looked down to see Blackfire has crawled to him, a scowl on her face and angry tears.
"You...you woman plowing dick. You just...took me by fucking surprise...is all."
"Well I needed to, or else I might've died from your sibling rivalry. But if you really want me to prove how much of a woman plowing dick I can be, I can oblige for both of you!" Robin gently pushed Starfire down onto her bed and flipped her onto her back while picking up Blackfire so that she was on top facing her sister, and then he just proceeded to screw both girls interchangeably as he either thrusted into Starfire, Blackfire, or missed both as he went in between and rubbed against their clits. "So, how do you think of this display?!"
"Augh, no fair! You can't pleasure both of us! That's cheating!" Blackfire complained, but her face betrayed that she was straight up enjoying this. "I'll never admit defeat to your dick!"
"Oh Robin, yes! It feels so wonderful! I can feel it coming again! Give me more!" Starfire pleaded her boyfriend.
"What's with you, you cum-dumpster of a sister?! How can you enjoy this with no dignity or shame?!"
"Because I love him and his dick, and from the looks of it, you are enjoying it as well, sister! Robin, I want your sperm! Your essence!" The orange skinned titan cried out, tears of happiness streaming down her face as he gave her sex that never felt so raw before. The Titan leader just went faster and faster, the stimulant overclocking his body past normal limitations even by his standards as he almost had sex with two girls at the same time in the sense like he fill both their pussies at the same time. Blackfire could barely hold it together as she gripped her sister's bosom, trying in vain to not lose to a mere human.
"No-no more! I can't take it!" She cried out, just wanting this amazing humiliation to be over.
"Yes, yes! Do it Robin! Give it to me!" Starfire nearly demanded, almost never wanting this to stop. They all, including Robin, screamed as they all climaxed, Robin spraying his white goo in between Star and Blackfire, covering both their fronts in semen before he started to fall back due to the adrenaline wearing off, and fast leading to a crash. He was still cumming as he fell back and thus covered Blackfire's butt, back and hair in his essence before hitting the floor and blacking out. At the moment, all three were in their own blank out as the two sisters were so hot and satisfied while Robin was just straight up knocked out.
30 minutes later
"Well, while he might've need a boost at the end, I guess he did adequate enough." Blackfire shrugged, unwilling to fully admit she was absolutely floored by the Boy Wonder and his extending pole. She was wearing one of her sister's uniforms since hers was destroyed by her own hands.
"Now do you see that he is worthy? Will you now leave him alone and let us love each other by ourselves?" Starfire asked her sister, whom rolled her eyes.
"I guess. Might as well let you have a boy toy that you'll just treat like a baby. At least no children will biologically come out of this."
"Oh, even if it is the impossible, if we did have children, I would love them so!" The jubilant titan smiled at the thought, while her sister scoffed at the idea.
"An Earthling/Tamaranean niece or nephew? No thanks. Well, I might as well get out of here. I reek."
"You could use the shower here."
"Nah, I don't want to smell like whatever berries or flowers you may have. I'll perhaps just clean myself by flying through the ocean or shower in space. Bye." Taking her leave, Starfire looked down at her zonked out boyfriend and sighed happily.
"Oh Robin, even though sister has done the butting in, you still provided plenty for me. I love you so much." Taking her loving leader to his bed while making sure nobody saw them, she laid him in his bed and kissed him on the forehead.
A/N: Whoo. I was wondering how to do this without diving into a kind of forbidden taboo, but I can say I did a suitable threesome with sisters without making it squicky. I hope I kept them all in character to your liking. I believe I did a good job but you know, a person can be their own worst critic. Leave a review down below. Thank you.