A/N: This is the end of Not My Sins. While NMS will remain Part One of Not My Sins the series aka Sins Verse, the C1 desination might change if I write something pre-NMS (Like something about the twins' mother or the MIT years for Tony)

Steve knew that his brother wasn't a fan of sparring, but Steve had a philosophy; if he was going to be his brother's semi-permanent body guard, along with looking out for his dad, then Robin would know basic self defense. Given that their mother had only let them do activities so long as they both were involved, Steve knew Robin was proficient in basic martial arts. All Steve had to do was keep him in shape.

They had the perfect place to practice too, at the Malibu Mansion. Tony had redecorated one of his lounges into a room where they could box, or spar, in comfort. It had a great view, but Steve didn't often stop to admire it. He was busy getting his brother to throw a proper punch.

"Come on, Rob," Steve exclaimed, "You have to put your whole body into the punch. You're telegraphing it, yes, but no matter where you have connected, you'll leave a bruise at the least."

"I don't want to hurt you," Robin replied.

"If you land that hit, then I need to be hit," Steve told him. "Just throw the punch like you mean it."

Robin reared back and threw himself into a right hook. Steve started to raise his arms when he went light headed. The room spun and began to grey out. Then Robin's fist connected with his shoulder, the pain of the punch jolted through him, snapping him out of his dizziness, but not before he hit the ground.

"Oh bloody hell," Robin breathed.

"Steve, what did you do?" Tony demanded from somewhere outside the ring.

"I'm Steve," Steve told his dad as he rubbed his shoulder. Whatever experiment Robin had been waiting for must have been completed. "Nice punch, Boy Wonder. It only took you half an hour to do that."

"Are you ok?" Robin and Tony asked in unison.

"Fine," Steve replied, waving his hand. He started to push himself up, and the room began to spin again, "Or not." He sat back down.

"What happened?" Tony asked.

"I got dizzy," Steve told them, "I'm probably just dehydrated or something. It's nothing to worry about."

"Then why are you rubbing your chest?" Robin asked.

Steve glanced down in surprise, "I honestly don't know," he said., dropping his hand. "It doesn't hurt anymore than it normally does."

"Have you been having dizzy spells often?" Tony inquired sharply, an odd look on his face.

"A few," Steve admitted, "but I'm sure it's nothing. Probably just tired or something."

"Why didn't you say anything?" Robin demanded, "Something could be wrong."

"I'm fine, ok," Steve insisted as he forced himself up. "I just got dizzy for a moment. I'll drink some water and we can get back to your lesson."

"No," Tony said firmly, "Steve, I need you to come down to the lab. Robin, go take a shower."

"Yes sir," the twins replied in unison. They both ducked out of the boxing ring, with Steve grabbing a water bottle as he got down and Robin heading for the bathroom as quickly as he could.

"What's going on, Dad?" Steve asked as he drank the water.

"How long have you been having dizzy spells?" Tony asked, turning and heading for the workshop.

"A couple of days," Steve answered, "the first one was last week. I was putting away a book in the library."

"That's not entirely accurate," JARVIS announced. "You nearly fell in the shower the Saturday before last. You claimed to have been light headed then."

"In the shower?" Tony repeated, "Steve?"

"That only happened once," Steve insisted.

"JARVIS?" Tony asked.

"To the best of my knowledge, he is correct," JARVIS replied, "although he has cut his shower time in half at least."

"Thanks for timing me," Steve muttered. "I'm sure it's nothing, Dad. I'm fine."

"I doubt that." Tony called over his shoulder, "I've, "I've been having dizzy spells too. For two weeks now. JARVIS and I are going to run some scans on you, and then we'll both do a blood test. Robin will be our control if we need him to."

"What do you think is going on?" Steve asked.

"I don't know," Tony admitted after a long moment, "but we'll figure it out."

"Surely you have some thought," Steve pushed, "an idea, a suspicion? Should I stop working out? What about the Iron Man project, are we putting that on hold?"

"Steve," Tony snapped, turning to glare at him. "I. Don't. Know. I don't have a guess or a suspicion or anything. Let me run some tests first."

Steve hesitated, "Sorry," he muttered.

"It's ok," Tony told him, taking a deep breath. "You're worried and I'm worried. Let's just get this over with."

/...`\\\

The tests Tony ran were pretty much the same basic tests Steve had gotten at the doctor's office every year of his life. All they could do was draw their blood and watch and wait for it to be scanned.

Tony was working on parts to the Iron Man, when Steve told him, "I'm going to take a shower." He didn't wait for his dad's acknowledgement before heading upstairs. Tony had a habit of not paying attention to people when he was upgrading or building things and Steve had learned over the past three months to adjust and deal with it. Robin could be almost as bad, in fact, so it wasn't like he hadn't had experience in living with a scientist.

What surprised Steve when he got upstairs, however, was Robin facing off with a man Steve had only seen through security cameras. "Doctor Goodfellow," Steve called, wishing that he'd known to grab his gun.

"Steven," Robin said, "this is Agent Coulson."

Steve placed himself neatly between Robin and the agent, offering his hand, "Good afternoon, sir. We were unaware that Doctor Stark was expecting guests."

"Doctor Stark?" Coulson repeated.

Steve stared at him for a pointed minute before turning, "Doctor Goodfellow, might I remind you that we are leaving in the morning to return to England?"

"Right," Robin said, with a nod. "I do need to do some packing." He turned and walked away.

Steve turned back to Coulson, "Is there someway I could help you, Agent Coulson?"

"I need to speak with Mister Stark," Coulson replied.

"Doctor Stark is in the workshop," Steve said, "JARVIS will inform him of your arrival, but I wouldn't expect to see him for a while." He gave Coulson a charming smile, "Engineers, you know. They never notice unless its about to explode."

That said, Steve turned and headed back towards the guest wing. "I didn't get your last name," Coulson called after him.

"I didn't give it to you," Steve replied over his shoulder without slowing down, "I thought it was bloody obvious."

Stopping by Robin's room, Steve stuck his head in and said, "Hey, want to mess with the agent's mind?"

Robin eyed him as he folded his shirts into his suitcase, "Do I actually have to do anything?"

"Stay out of sight." Steve gave his brother a charming grin not unlike the one he'd given to Coulson.

"Just don't get arrested," Robin told him pointedly, opening a drawer and beginning to empty it.

"I won't," Steve promised. He paused to take note of what his brother was wearing and headed off for his shower. There were always bonuses to being identical twins.