Token warning for kiddie incest
Her hands are softer than his, and her skin is just that little bit fairer, because she's been cooped up inside all day practicing her letters and perfecting her needlework, and he's been outside in the sun, beaten black and blue by wooden swords. He has a talent for swordfighting, but they've got years and years of experience under their belt and he is too rash, too easily distracted - he's just a boy with the smell of summer clinging to his skin.
"You have to be quiet," she murmured as she ran a finger over his lips, and he nodded. He didn't think that what they were doing was necessarily wrong, but he knew that mother and father would be angry if they found out. But he loved her, and she loved him, and they knew each other better than anyone else in the world because they were the same person split into two, and this was the only way they could be whole again.
She rolls him onto his back and he looks up at her. She smiles a little differently - more delicate, less devious - and she straddles him as she pulls up her dress and starts to undo the lace that was holding it all together. He has an easier time, toeing and kicking his boots off, pulling his pants down.
They were naked and she was lying on top of him, and the only difference between them was that she didn't have anything between her legs and he did.
He'd been good about keeping quiet until she got him hard with her hands. He was panting as she slipped him inside her and moved her hips. She slid her small hands into his thick hair and pulled pretty hard, but it didn't hurt. It'd been uncomfortable and strange the first time but that was months ago. The twins have got it all figured out now and everything just felt right.