Nat was in her room. She had already changed into her pyjamas when Steve knocked on the door. He came in quietly and walked to her decidedly. As soon as he was close enough Nat gently grabbed the back of his neck and pulled him in for a kiss. He grabbed her by the waist, bringing her closer to feel her body against his. They pulled away from the kiss, locking their gazes for a few seconds. She smiled and Steve brought her in for another passionate kiss. He picked her up as she put her legs around his waist. Steve brought one of his hands, from the back of her waist, slowly down to her butt. He walked a bit more and gently placed her down to the bed. Nat ran her hands under his shirt, feeling his abs, and took off his shirt, almost without breaking the kiss. Steve slowly undressed Nat, tracing her body. He let his hand wonder, followed by kisses, covering every inch of her body, from her neck to her belly. He slowly took off the rest of her clothes to be able to kiss the places he hadn't kissed yet. Nat placed her hand down his chin, bringing him up again, before their lips touched. She grabbed his back and gently brought her hands to unlock his belt. He quickly took his pants off and they gave into each other.
Steve reminded her to be quiet, 'cause they were in the Avengers tower and the others were downstairs. But slightly out of breath she told him she couldn't be quieter. When they both reached their climax, they released with a last passionate kiss. And fell asleep cuddling.
Later that night, Steve woke up thirsty and got up without waking up Natasha. He headed downstairs got a cup of water and went back to sleep, this time in his own bedroom, being as quiet as he could, without waking up his children.