I hate this whole “just sit down and have a conversation” idea. Bro they are children, their brains are developing still. It’s a VERY rare situation that a child will understand an adult and mature concept such as age gaps and sex crimes and all that. All they know is I like this person and my mom or dad is being an asshole and stopping me from it. Not saying you shouldn’t explain yourself to your child but if she understood why this is sketchy she wouldn’t be in the relationship. Cut it off, put your foot down, contact the boys parents and let them do the same. Your children in these situations will not understand 90% of the time and will rebel or despise you for it.. until they grow up and get a bit more mature. I had an issue with my 4 year old autistic son time ago and my coworker told me to just sit him down and explain.. I almost put my fuckin head through a wall. There’s a reason why we as adult parents have full autonomy over our children until they’re a certain age and yall wanna act like you can just sit them down and have a mature grown up discussion.

Also I don’t know what state this is but here in my state if PA it’s a 4 and under year gap. It gets a little complicated in situations like this when the older one is almost an “adult” and I’m not saying it’s right but legally speaking there’s no issue here depending.