Nice parents isn't a guarantee of nice kittens, that's true - but like spid says, some behaviour does seem to run in the family. Whether it's "nature or nurture", ie whether they're genetically predisposed to being friendly/mean or learn it from watching mum, I don't know. But I know I wouldn't breed from an aggressive cat just like I wouldn't breed from one with a genetic illness.

Having said that, the last litter of kittens I had started doing things that their mum hasn't done since she was a kitten and therefore they hadn't seen her do - such as taking a flying leap onto your shoulder to chew your hair, or sucking their own tails when they're bored (which they too grew out of). None of my other adult cats do those things. And I know they're not unique things and that many other cats and kittens do them, but the similarity to momma-cat was really striking.

dagny0823 - I would take everything into account, personality as well as phsyical attributes and health. Your neighbour's cat sounds like a good option as he's not been able to go outside and have his way with every girl in the neighbourhood and catch anything nasty! Saikou raises a good point though, he might decide to act more like a man once he realises what he's been missing - eg spraying in the house, becoming a bit more aggressive etc.