Looking for a Tony/Bucky fic
I'm looking for a Tony/Bucky fic with a one-sided Steve/Bucky. I'm pretty cure its a ABO, and at the start Steve and Tony are mated or bonded. Bucky comes to live in the tower, and Tony welcomes him to the Pack with open arms. Steve breaks the bond with Tony, so that he can be with Bucky, but this absolutely horrifies Bucky. Steve tries to say that it’s okay to break bonds in the 21st century and they can be together, but Bucky is having absolutely none of that. Instead, Bucky makes it his mission to look after Tony and sometime after that I'm pretty sure they get together.
I think this was on ao3.