Mine are mostly all related. We had 3 to begin with, two girls (Momo and Lady) and a boy (George) 2 weeks after DD was born in 2011 Momo had 6 kittens, 3 weeks later Lady had 4.
DH fell in love and we ended up keeping 2 boys (Suru and Lennon) and 1 girl (Shinobi). Shinobi had 5 kittens but 3 died with 48 hours and we couldn't bare two separate the two kittens, so we kept them (Pixie and Bumble), and then Bumble had kittens, and we kept two girls, Narla and Cici.
Unfortunately we have since lost Lady and Narla. We did try and introduce a kitten when Pixie and Bumble were little (was actually their cousin) but the clowder wouldn't accept her so my friend took her back.
Then in September this year we got 2 brothers and introduced them very slowly and the clowder have just accepted them in, was nice to see all the hard work pay off. I have 4 outdoor cats, Momo is allowed out but she just doesn't want to. We're working on getting Pixie outside but she's not keen. Cici actually has allergies and she doesn't get on very well with grass, not good when we're surrounded by fields. The boys will be outside cats though. Bumble, actually suffered brain damage at birth and has no sense of balance and she gets scared by her own tail, so outside just won't be safe for her, how she had 4 perfectly normal kittens is beyond me.