Blurred (слэш)

The Winter Soldier and Bucky Barnes are two different people sharing one body.... and one boyfriend.
Tony loves both suave, charming Bucky and also broody, dangerous Winter and both men love him too. But the shared relationship is blurring their personalities until it's hard to stay separate. They switch without realizing, causing memory loss and confusion, anger and even a little jealousy when private moments with Tony are interrupted when the other comes forward.
If Bucky and Winter blur too far together, one will be lost forever, his mind and consciousness erased so the other can exist alone, and Tony is terrified of losing either of the men he loves.
Winter's willing to go since he was created from torture and used as a weapon for decades. Bucky's willing to go because he's tired of seeing a weaponized super soldier in the mirror when really he's just a kid from Brooklyn.
They have to separate before it's too late, but even with Dr. Cho's help, it's a risky experiment almost certainly doomed to fail.
How can Tony possibly decide which of his boyfriends he'd be willing to lose forever?