Can my character be in a relationship?
Backstory yes. Played-out romance no.
Your character can have a husband, a wife they buried, someone they're still looking for, a complicated history. That's characterisation and it makes people worth meeting.
What isn't allowed is playing romance out as an ongoing thread: dating RP, flirting scenes, anything sexual. Not in channels, not in DMs arranged through this server, not in-game. That's rule 2.4.
The reason is simple. We're 16+, which means adults and minors share these channels. There's no version of that which is fine, and no fade-to-black exception.
If two characters care about each other, play the loyalty. Play the worry when one of them doesn't come back. Play the person you'd cross a red zone for. That's stronger RP than a romance plot anyway.