AITA for firing an employee after I went over the rules twice?

Our family runs a very successful business and part of that success, is having rules. We like to keep the same staff for a long time, and we have, and I'm sure a significant part of that is one of our rules, no dating your coworkers. This has been a rule for years and we've never had any problems.

My son (19m, and an employee) has a lot of confidence and will ask out anyone he finds attractive and he thinks is gay and around his age. We hired this young man (20m) that we figured was gay, and we went over all the rules with him like we did with everyone else. Then my wife pointed out that he's spot on our son's type, so to be safe we went over the rules with him again. And as soon as my son saw him, I told him no.

It's been two months, they didn't listen. I fired the young man. AITA?