I believe (I am sure someone will correct me if I am wrong) that the vast majority of Israeli mathematicians start their PhDs close to that age. The Israeli school is extremely strong (however, as my Israeli friends point out, that might be the reason for why they concentrate in combinatorial fields -- much less baggage than in, say, Algebraic Geometry).
And to add to the list of examples above, Joan Birman started her degree after raising her kids at a time were women did not had a pretty hard time, did very well afterwards, and is very active today (and she is even older than the OP)
