Lol, yeah.
Haha, don't you read the forums on ijji? xD
Or try clicking the "Help" button in-game. Lawl.
From what I know:
-Max 4 family members, and you can add 2 more as guests, but not permanent members~
-Characters lower than lvl 30 are automatically added as guests to a random family when they log in~
-After an hour of playing (it shows the percentage on the family stats/J), you'll get a family gift...it could be a set, a title, or maybe some more stuff that I haven't tried yet...they're limited for only a few hours to a few days...max I've had was 3 days or something for the title~
-You get extra exp % ranging from I think... 10% to 30%...based on what I get...I don't remember if it goes up more than 30%, but the % of exp depends on how many members are online, I think~
Well, that's all I can think of now. I hope it helps. ^_^