They'd wound up in a position where they'd both been able to find their way back to love with others although when they'd parted ways that day Bucky hadn't been so sure he'd be able to find it again. After everything with Steve, he'd gone to both Natasha and Clint to tell them how he felt, knowing the two of them had already found each other and that he likely wouldn't have anything to show for his honesty other than the knowledge that he'd been open with the people he cared for and could say he put himself out there to the fullest extent. For a time after that he'd been terribly lonely, sad, and resided to the fact that he was going to stay alone. Thankfully it hadn't ended up like that, but there was a stint of time where he believed it would.
In the end, Clint and Natasha had come to him with the idea of them all trying this relationship out together because neither of them had wanted to let their feelings for him go. And that, well, that had meant everything to Bucky. He was important enough to them both that they were letting him into the life they'd started building because they wanted him to play a part in it.
Hearing that Steve loved Tony and assuming then that things were really working out for them, Bucky was glad for him. He meant it when he said all he'd wanted for so long was for Steve to be happy. If they could now both be happy and be happy for each other, then there wasn't much more they could ask for at this point.
"No, wouldn't want that," he agreed. He looked up at Steve again, away from the two dogs who'd become best friends, it seemed. "It's gonna be okay now, Steve. We are, I mean. We're okay."