DNA - the point for me is that it is bringing me nearer to finding out who my g.grandfather was. I know he lived with g.gran from mid 1880s onwards (my gran born 1884) and he died in 1935. I have photographs of him too. But his origins are a total mystery. He didn't marry g.gran so no marriage cert, although I think he may have been illegitimate and Jewish so a marriage cert probably wouldn't have helped. It's possible his mother was called Da Costa, but when my gran died her eldest daughter who lived with her burned all the photographs and paperwork relating to this Da Costa lady saying "We don't want to know all about that do we?" Whether it was because she was Jewish and that was a touchy subject just after the war, who knows?
Anyway I have been in touch with a 4th cousin in USA (via DNA and 23andMe, not Ancestry), who is Jewish and I'm now researching all his family to find the missing link. Hopefully, I'll get there in the end, if not at least I know I was right about the Jewish connection.