I like the "settle down, get married, have kids" ending for Ed in "Fullmetal Alchemist" because it suits the themes and the character arcs well. But also because there's still plenty of room for adventure beyond the joys of a simple life (it is fun to imagine Ed picking up a million homesteading-related hobbies with all his usual competitive spirit); Winry has a thriving career! She and Ed can travel around the country, visit people, and probably even visit Xing before kids or when their kids are old enough for travel.
But I also like it fine because I feel 100% certain that Edward Elric would not have children unless he was 100% certain that he wanted them and was ready to be a good dad. He would not bring life into this world recklessly. I feel like he would have asked himself, "Is there any chance I might be a deadbeat dad?" and that he was absolutely ruthless with his analysis of his character, like, to the degree that it quickly stopped being funny or embarrassing and started being sad. He'd try and get his own Riza Hawkeye about this: "If it ever looks like I'm being a shitty father or husband, I need you to kill me," he says, sleep-deprived and panicking, and Alphonse can only be like, "Brother... No..."
Also, I feel like we shouldn't leave Winry out of this. This woman is driven and successful and was orphaned because her parents left her for a good cause. She and Ed would sit their asses down and have an excruciatingly thorough and detailed conversation about parenthood and their future. I could buy an AU where they mutually decided to be childfree, sure, but I cannot be fully convinced that they as a team would be reckless about children and parenthood.
I'm sure they'd make mistakes, of course, as all parents do. (I also feel like they would try and make plans with the same focus as automail schematics and alchemic circles, which would often be immediately ruined upon contact with the "enemy". And that Uncle Alphonse would shamelessly and mischievously spoil his niblings against parental wishes whenever his brother's back was turned. Traitor.) But they're also one of those couples where I see them in the cliché "happily ever after" and I can genuinely be like, "Yeah, they're fine."