That's right, this is what my family would be like at Thanksgiving if fandom ruled the universe. This is no way based on how my family is set up, just how I think this would make sense.
My father: Jean-Luc Picard.
Really, who didn't see that coming? Through most of TNG Picard never really wants a family, you have to admit he is good father material. He'd be supportive, he'd always have a story, and maybe I'm biased because Patrick Stewart is bald like my father but that part doesn't hurt either. All that aside, I would love to see Picard carve the turkey as the family gathered around.
My mother: Wynne from Dragon Age
I'm going to be honest guys, this one is hard. I didn't want to get too obvious, which would've been another Star Trek character (or several). After playing more of Dragon Age last night the protective instincts of Wynne made her a strong choice. Also I'm hoping her studies of herbalism make the seasoning on the sweet potatos that much better!
My older brother: Riddick from Pitch Black
Riddick is a great choice because he's the older cooler brother that you know you'll never be as cool as, so either you try to fit in with him or your stop trying. Of course, I don't think I'd try too hard to be as cool as a murderer, but you never know.
My younger sister: Kaylee from Firefly
Cute, spunky and smart, Kaylee is the perfect choice as a younger sister. If you've seen the show you know exactly what I'm talking about. If you don't, imagine if car mechanics were mostly my little pony fans. Yeah, weird mix of cute and mechanically smart.
My cousin I would go on hijinks with: Vyse from Skies of Arcadia
Vyse would be the best cousin to have because he would always find something fun to do. Also, wouldn't it be great to be an air pirate on thanksgiving? At least in pretend when I'm 8 years old in a cardboard box as a boat sense.
My crazy Uncle: Solid Snake
Who doesn't have a crazy uncle talking about conspiracy theories to some degree or another? At least Uncle Snake could confirm these theories with his "to-do" list. I'm sure he'd be the best to carve the turkey too... with an assault rifle.
My Grandpa: Hari Seldon from The Foundation Series.
I know this one is probably coming from left field for some of you. If it is, go read Foundation by Asimov right now. Hari Seldon ends up inventing a science to predict the future of the masses. It's a combination of psychology and statistics called Psychohistory. The wisdom needed to make something like that has to be HUGE. I would listen to him talk while I was eating delicious turkey.
My Grandma: Princess Peach
I understand she is a lot younger than a grandmother is thought to be, but she has a lot of the same qualities of a grandmother. She's sickeningly sweet, ultra feminine, has huge hair and is pretty good with a frying pan from what I see in Super Smash Bros.
And that's my geek family. :D