Question on Japanese family names

[Green Airplane]

Hello,
I've just come across a surprising fact. Saito Hitohiro Sensei (Aikido, Iwama Shinshin Aiki Shurenkai) has his family name spelled differently from his father, Morihiro (though they apparently have the same pronunciation).
Hitohiro Sensei's name is spelled　斎藤仁弘 (according to his dojo's homepage, http://www.iwamaaikido.com/)
whereas his father's name is spelled 斉藤守弘, I've double-checked it with one of his books from 1973.
The kanji 斎 and 斉 are different, albeit very similar and pronounced the same way.
Is it common for the Japanese to give their children different family names? Or is this some kind of anomaly? How frequent is this phenomenon?

[gerald_ford]

I think this is pretty unusual, as I've never seen it done that way. I do wonder though if one kanji is the more archaic version of the other, thus they're actually the same ones.

For comparison: http://www.saiga-jp.com/cgi-bin/dic.cgi?m=search&sc=0&f=0&j=%E6%96%89&g=&e=&s=&rt=0&start=1&sid=1239719628_773