Dilemma, any advice please

Hi all I recently got told from my ex husband, that my new partner’s ex wife, has slept with a lad half her age.. she has told my ex not to tell anyone and his mate told her not to tell my ex.. Yep it’s confusing!! The lad in question is the son of a friend of ours.. This lad also has a partner who has just found out she might be pregnant, he doesn’t know this. I’ve suggested to my ex that he asks the lad in question if it’s true as the women is known as a liar. Your thoughts please

Is the lad she slept with of age? If so, my advice is mind your own business. If not, then having someone talk to the parents of the lad might be the best route to go, and let them parent their child.