Ha! I'm right in the middle of re-reading the perfect story for your request. Lauralot's series "Alexander Pierce should have died slower" can be found at AO3. In addition to having the assassin personality, Bucky has been trained by Pierce to be Daddy's boy, with children's toy, punishment, and sex. After Pierce's death, Bucky needs a new Daddy, but is confused when Steve doesn't allow him to...um, pleasure him, to put it mildly. Steve is very touchy-feely, very happy to have his best friend back, no matter the state he's in.