This isn't vital to my story, but it is a side fact that I just wanted to confirm before I went ahead. According to the Black family tree, Bellatrix Black was born in 1951, which means she would have entered Hogwarts in September 1962/63 and left in June 1969/70 (depending on her month of birth). In the books, I believe Sirius notes that Rodolphus and Rabastan Lestrange were both contemporaries of Snape, part of his gang of Slytherins.

If this is true, then that would put Bellatrix at least seven or eight (and as much as ten) years older than her husband Rodolphus? Is that correct?

I don't find this hard to believe, given that both came from pureblood families that probably arranged for their children to marry. I just wanted to confirm this, though, because it has the potential to define their entire relationship if Bellatrix was a Death Eater for most of the 1970s and then married someone who would have seemed still virtually a schoolboy to her towards the end of the decade!