Steve's life is the same as usual. He goes to work, fights super villains, banters with other Avengers and goes home to an empty apartment. Until the son of an old friend shows up asking for help, well sex first, then help. Suddenly Steve is married, fighting super villains, worrying what Obadiah Stane and coming home to Tony most nights of the week.
Steve gets into a serum-enhanced rut. Tony figures that there’d be a long list of people who’d volunteer to help Steve out, but there’s only one person Steve wants.
When Steve goes into a rut while he and Tony are kidnapped by Hydra, Tony is convinced that what happens between them is going to ruin everything. He's wrong.
Tony knows that something like an arranged marriage would happen to him eventually, like it does to all omegas. He also knew that it would happen because of Howard. The fact that he’d be unwanted shouldn’t have come as a surprise.