Mom was complicit too. Somehow he made it worth her while to permit him access to the children. She was too busy or too selfish to look out for her child. Sorry, that's what I see. Predators have over and over again explained how they cozy up to children. All they need is access.
Children NEED to be taught at an early age, DON'T LET ANYONE TOUCH YOU, AND THEN TELLS YOU NOT TO TELL ANYONE !!!!!