Both of these parents are extremely well-known in their fields.
At the time, Beauty and The Beast were each married to other celebrities, but had an affair while working on a project together.
Beauty was just becoming well-known at the time, and having a baby with a famous and married music icon while each was married to someone else would have hurt everyone’s careers. So, when they discovered she was pregnant, both couples agreed that Beauty would take a little time away from the spotlight, and Beast and his wife would publicly pretend to be pregnant.
Beauty and her husband separated because of the affair, but Beast’s wife stood by him and raised the child as her own… even though Beauty and The Beast have hooked up several times since then.