Slightly tongue-in-cheek, but thinking about it I can't think of a single* main character in any of the Star Trek shows who is married with kids. And yet in the traditional Navy (and other armed forces) it's common-place. In TNG we even know Enterprise is bigger to hold families but they are 'civilians'.
*OK as I write this I think of some exceptions, but none are a full family unit:
- Beverly Crusher obviously has a son... but is she married?
- Neelix has a normal family setup, for his species, but it is shown as a novelty due to so many differences to our norms
- Sisko has a son but again isn't he separated?
The main characters are typically not in their early twenties but mature, established officers. People who often would have families even though they might not feature in the show.
Are there any happily married Star Trek characters? It seems the only time characters have families or spouses, these are in some way dysfunctional or sources of strife, for the purposes of narrative.