Based on this prompt from graellora on Tumblr: "Olicity: 'You are THE woman I love.'"
This would be set long in the future, after they get together and after Oliver finds out he's got a kid out there.
"How was the train ride?" Felicity asks, not looking up from where she's preparing the ingredients for dinner.
"Long and crowded," Oliver says with a sigh and then sits in the bar stools on the opposite side of the kitchen island. He loves watching her cook, or just watching her really. He hates being away from her, even for the smallest amounts of time. The fact that now it's only to see his son in Central City is the only thing that makes it bearable. "Don't ever tell Barry this, but I wish I could travel the way he does."
"Ugh, of course not," she says with a laugh. "We'd never hear the end of it."
"How was your day?" he asks, leaning on his elbows. "I called to check in on things and Digg said you had to leave for a bit."
"Oh, yeah," she says, eyes darting to look up at him a moment before returning to her task. "Just a work thing. So how did Connor do in the game?" she says, almost too brightly, clearly trying to change the subject.
"He was great," Oliver gushes. "Just like me at that age. Total ball hog, confidence beyond his abilities—doesn't help that he somehow managed to score a goal."
"Really?" Felicity replies, smiling broadly, equally proud.
"Sandra and I went nuts. I think we frightened the other parents. He could barely keep playing he was so excited. I took the later train so we could take him out for celebratory ice cream after."
"That's great," she says, smiling as before, but this time it seems forced, practiced. She looks back down at the food she's preparing, her forehead creased, and Oliver tilts his head in concern.
"You OK?" he asks.
"I'm fine," she assures, not sounding at all reassuring.
"Felicity," he prods. She pauses a moment and then looks up at him, nervous and unsure.
"It's just..." she starts and then takes a moment to think before continuing. "Do you ever wish your mother hadn't did what she did?"
Oliver crosses his arms in front of him, surprised she would bring this up, and then answers. "Of course I do, but I understand why she did it even if it was wrong. I can't change the past and I won't hold a grudge against her."
"No, I know," Felicity says, sounding apologetic. "That's not what I meant. I just...wonder if you wouldn't rather live in Central City. At least you wouldn't have to commute."
"Yeah, sure, but they're not in the market for another vigilante, " he says, trying to lighten the mood. "Our lives are here."
"Well, maybe yours should be there," she says lowly.
He pauses a moment, trying to process her words. "What are you trying to say?" he asks, standing and moving toward her around the island.
She sighs in frustration and brings her hand to her temple. "I don't know!" she exclaims, turning away from him. "It's just that you love Connor so much and you and Sandra never really got a chance to see if you could work. And sometimes I worry that I'm the thing keeping you from having the family you want." She turns to look at him then and Oliver is speechless. She swallows hard, tears beginning to well up in her eyes before she goes on. "Because I would understand, you know? You and I got together before you knew about Connor. I wouldn't blame you if you wanted to try to be with Sandra for him."
"I don't want that," he says, unable to understand how she could think he would.
"Are you sure?" she asks, gaze dropping to her feet. Oliver approaches her slowly, takes her face in his hands and makes her look at him.
"Felicity, I care about Sandra," the starts. "She is the mother of my child, but you are the woman I love," he says softly, with as much sincerity as he can muster. "I cannot even begin to describe how happy I am to have Connor in my life, but I am equally grateful to have you. After everything we've been through, I couldn't imagine spending my life with any other woman but you. I love you."
She stares into his eyes a moment and then wraps her arms tightly around him, burying her face in his chest.
"I love you too," she says. "So much." Oliver smiles and rests his chin on top of her head, closing his eyes, unable to imagine how he could be any happier with his life. But then Felicity proves him wrong as she says, soft and small in a way that's so at odds with the meaning of her words, "I'm pregnant."