He wasn't the son of Holocaust survivors, he was a Holocaust survivor himself. The comics back in the 60s even made him be a late bloomer so his magnetic powers could manifest in his captivity; most mutants get their powers during puberty, but his didn't show up until his 30s. The 2000s movies, of course, just had his powers manifest at the normal time, since they could manage that.

I'm sure the MCU version will have to adjust that somewhat, since the timelines no longer quite match (unless they make him immortal or something).