Continue chat with my ex friend's son?

So one of my very good friends for two decades randomly ditched me years ago. Never contacted me again. It truly hurt. We were such good friends.
Ive finally moved on from the hurt, but her son who is now in their early 20s sometimes messages me. I used to babysit him when he was 10. He told me last year on a message that he liked me, romantically. I wasn't sure how to reply but have chatted off and on as friends.
I am unsure to continue...I do talk about casual things but I don't know to keep chatting or what. I know he is a good kid I just am unsure going forward. Thoughts?