I've been dumping hours into Fire Emblem Awakening, grinding to increase relationship support ranks between every character just to see all of the skits it unlocks. It really gets you to care about all of the characters, even the ones you'd otherwise never use in battle. The writing is sharp, clever, and often pretty hilarious (8-4 did an amazing job with the localization). Of course, this sort of thing seems right up Double Fine's alley, but it would be impossible for a game that doesn't have any real set characters. I'm very curious to see how this ends up getting handled in MASSIVE CHALICE.
The FE:A marriage/support mechanic is super rewarding. The higher your support rank, the higher the stat boosts you get when the two characters fight next to each other. I've had several times where a husband or wife was about to die to an enemy, but their spouse jumped in and blocked the damage to save them. It's just incredibly satisfying.
The way children are handled is fairly simple. The child inherits one skill from each parent, which allows the child to learn skills from classes it otherwise wouldn't have access to due to gender or other reasons. There are some incredibly unbalanced skills that discourage experimentation with character builds, so the system isn't perfect, but I was very excited when I heard you guys were planning mechanics similar to this!
Hope some of that was helpful! I highly recommend the game. It's been getting a lot of people interested in the tactics genre.