Anyway... Some mmorpg has marriage system (player to player) but I suggest adding the ability to marry a member of your household (family!?! The term household is definitely not FROM A CERTAIN ANIME!?) member.

Your main chara can only do this (add a main chara selection system), marrying is like a quest, you need items and silvers (black pearl?).

Marrying acquires certain buffs, positive personality traits.
After marrying, you cannot delete the chara involved.
Edit: Ow... After marriage... You cannot edit your household member. (So you can't make him / her ugly and make that an excuse to divorce! Kidding!!! But seriously add that... if you plan to execute this. Main chara? You still can.)

Devorcing will make your household member (family) to run away, gone, for good, meaning that chara will be deleted.
Has a high chance to obtain temporary or permanent personality trait/s.

Personality traits? See my other suggestion.

Oh... This will ignite gender issues... Nvm. Just a suggestion.

Right now I'm just idling.