That's rubbish.
Anne had affairs - she married one of her affair partners. Mark Phillips did also and had a baby with another woman. AFAIK Charles only had one affair, with Camilla.
We knew Diana had affairs because the press exposed them. I'm pretty sure the Queen couldn't have risked an affair and I can't see her wanting to. I'm not convinced Philip did either. Margaret did, Fergie did. That's only the more recent royals.
Both Charles and Diana admitted their adultery in TV interviews!
I don't know where you got that notion!