Im 90 percent sure I fathered a child with a former fling

Throwaway because my regular account reveals where I live

So, when I was 23, I (33M) met a woman named Amy who was visiting the city I live in. We hit it off and spent a week and a half having sex, smoking weed, and visiting the beach. By the end, I was in love. We both were. We talked about either her moving permanently to my city or me moving to hers, but it didn’t work out. I had just been accepted into grad school, while she had younger siblings and older parents, so she couldn’t leave. We considered a long-distance relationship but also decided against that. We did exchange numbers and social media. We texted each other for a few weeks after she went home, but she abruptly cut contact. She said that a guy she knew had asked her out. I was bummed out but wished her the best. She didn’t unfollow or block me on social media, though. I don’t know why—maybe she forgot or didn’t see it as a problem as long as I wasn’t messaging her, which I didn’t. But sometimes her posts would end up on my feed, and I would occasionally check in on her.

Several months after she ended things, she made a post showing her, her boyfriend, and their new baby boy. I immediately suspected I might be the father. The timing was right, the baby sort of looked like me, and we did have unprotected sex since she said she was on birth control. I decided against asking her if the baby might be mine. For one, I wasn’t in any state to be a father, being a student working on my master’s and working part-time. And I figured, well, even if the baby was mine, she had found a guy to raise him, so it’s not like I was leaving my potential son fatherless. If she wanted me involved, she could contact me. I unfollowed her on all my social media and moved on with my life. I dated and eventually ended up in a long-term relationship with a woman I’ve been with for five years now.

Recently, my brother had a baby. He lives out of state, so he sent some pictures of his kids to me and our sister, Laura. We were talking about it, and I told her, “You know, there’s a non-zero chance I might be a dad.” She asked me what I meant, and I told her about Amy. Curiosity got the better of us, and we decided to look up her social media to see if there were any more pics of her kid. There were, and her kid definitely looks like me—almost like a clone. We found an old photo of me when I was about Amy’s son’s age, and it’s almost identical. To make sure this wasn't just me and my sister going crazy I showed the photos to some friends of mine and they all initially though they where the same person. Thats how similar they look.  

Me and Amy’s husband don’t look similar either. Of course, this could all just be a coincidence—me hooking up with a woman who later gives birth to a baby that looks like me 9 months later—but currently, I’d say I’m about 90 percent sure Amy’s son is mine.

Thing is, what should I do? She is still together with her husband, and even if Amy’s son is mine, I doubt they’d be happy with me intruding on their life. I’ve heard that some DNA tests will store your DNA, and if someone you’re related to also does one, you’ll be notified. I’m thinking of doing one or multiple, and if he ever does one to learn about his ancestry, he’ll know. Would that be weird? It seems to me like it’s the best way to “contact” him without disrupting his life.