I think you did the right thing. I would have done the same. It is always weird to hear from past relationships and sometimes things can take a turn you didn't expect when you open the door to being friends again.
I had, basically, a "friends with benefits" situation when I was 18/19. No bad blood between us, but it was a complicated situation at the time. We had a crazy good connection though, and I have thought about him often over the years, in a nostalgic way, because I am completely happy in my marriage.
About 10 years ago, he messaged me on FB. Started talking about our past. Asked how long I had been married. I told him "9 years" and he proceeded to say "Damn, I guess I missed my chance then, huh?" I was completely taken aback. This guy is a total player/ladies man type. I called him out on that and we had a bit of friendly back and forth for a few minutes. He has since remained my FB friend, but didn't engage me directly again until yesterday, when he started commenting on my post from my day at
Disneyland. He recently moved down here from Texas and now I'm kinda thinking he is trying to get in good with me again. It's honestly making me kinda uneasy. He has recently ended a long term relationship and that was also the case when he messaged me 10 years ago. I'm not sure what to think at this point, but I am treading very carefully with my replies to him.