Bucky doesn't know how it happened.
He only knows that he is glad that Steve is on the moon or wherever he is now for the first time because he would not know how to explain to him.
How do you explain that you have a relationship with your partner, the new Captain America, and the only man alive to beat the Avengers, now a newly pardoned ex-con.
Maybe if Steve saw how Sam laughs when he tries to flirt with him like he used to do before the war, before Hydra, before all that.
Maybe if Steve saw Helmut cook for them like no one has done since he lived with his late parents.
Maybe if Steve saw how Sam wakes him up from his nightmares with soft words and cuddles, letting him cry and throwing something away if necessary.
Maybe if Steve saw how Helmut gives him tea and strokes his hair without saying a word the mornings following those nights because neither Sam nor Bucky himself let him sleep with him on bad days, no matter how few, of Bucky knowing that the Sokovian is no match for a James raped in a nightmare.
Sam has markings that show that he is only slightly so.
Maybe if Steve saw Sam get up early to run with him on a good day.
Maybe if Steve saw how Helmut hugs him singing in Sokoviano when he has a bad day so that the night is not bad and the three of them can sleep together as they all want.
Maybe if Steve saw how cute Sam looks when he pouts when he doesn't get something.
Maybe if Steve saw how adorable Helmut looks with one of his Sam shirts and pants on.
Maybe if Steve saw how much he loves the two idiots, maybe ... maybe Steve would be proud of him.
Bucky looked to his right where his sleepy boyfriend watches him huddled against him.
-"Are you okay?"-
-"I am."-he affirms and after a moment, Zemo nods and lets himself be carried back to the world of dreams.
And Bucky ... well, looking at the two handsome men huddled against him on Sam's little bed from his parents' boat he decides that good ..
Steve might not be proud but he would be happy ...
..because he is finally happy.