Unsure of what to think

My son (11) was just introduced to his biological father a few months ago. (He contacted me; we were high school sweethearts together from 14 years old to 20 years old) He has been true to his word so far and staying very consistent with his visits (my house only for now with my supervision solely because he’s been away my son’s entire life) he’s apparently doing very well for himself in life now. He has also helped me in small ways that I did not ask for such as fixing my car when it drove funny, brought dinner by twice so I didn’t have to cook, etc. Yesterday, he dropped the bomb on me that “he still loves me” and “his biggest regret in life is not choosing me and our son.” I did tell him that I don’t have feelings for him anymore because I was really angry at him for a long time but I am extremely proud of him now and I hope he continues to be around our son.

It’s been hard for me to believe him in the past because at 12 months, he asked to come around, I said yes, he came to see him twice and I didn’t hear from him again until our son was 5. At 5 years old, he had not seen him but asked to come around and I told him not unless it’s consistent, because he just started kindergarten and I don’t want him hurt. I didn’t get a response back to that text nor hear from him again until a few months ago. This time though, has been completely different than previous times so I do believe he’s serious about staying in his life. I do believe that. I had no interest in anything romantic with him before he told me that yesterday, but now it has my head spinning. I don’t want anything ruined for our son. He deserves both parents even if we are only friends. I do enjoy his company when he comes to visit and he is still attractive, I’m just unsure if rekindling anything would be a good idea. I hate saying no and being the bad guy, but I feel like right now we should stay friends for our son like we have been the past few months. Would it be a bad idea to try a year or so into the future if things stay going well between the two?