Interesting thought, I'm not sure if it's possible, but if it happened like you think it would, we'd have "bloodlines" of wizards getting more powerful every generation.
We don't hear about family lines of wizards in the DF. (Maybe this should be part of another thread.) Harry is the exception in the series, so far. He knows his mother was a powerful wizard and he knows one grandfather, who is on the Senior Council. Long lived wizards can outlive their progeny; especially those who are born as vanilla mortals, and some wizards; like those who become wardens, have a more dangerous lifestyle than a wizard who spends most of their time doing magical research. So the wizard doing research could still outlive his higher risk taking, though magically gifted children. Add to this the secretive nature of being a wizard and you have a lot of people who don't communicate well with others, including members of their own families.
Of course we can put down our lack of knowledge of other wizard families to Harry's general isolation from the White Council for most of his life, but we do know a little about one other wizard. In Turn Coat Harry asked Luccio if she had family. She replied "Yes. Technically." ... "The men and women I grew up with...They've been dead for generations." OK, so maybe these people weren't her brothers and sisters, maybe she's talking about cousins, but it seems a bit cold to me. Perhaps that would be a natural adaptation to outliving so the people you grew up with, and many others you met along the way who aged and died while you kept rolling along, but it suggests that many wizards live somewhat dysfunctional lives by normal standards. Most of them must have a hard time getting close to others after they have been around for a while and gone through this cycle a couple of times.
