Paternity Question Help

Location: Colorado and Pennsylvania.

Back in 2011 I was active duty military and visiting Fort Carson CO I met up with a woman and her husband (they were polyamorous). Adding another person to the bedroom was a VERY regular thing for them. At the time I was informed she is on birth control or that he had a vasectomy. We had our fun, I used protection. The husband even joined us a couple times and then I left since my training was complete. We had briefly considered staying together in serious relationship (Talking about leaving her husband even) but things just did not work out. She sent back the few belongings I had along with a hand written letter stating she is pregnant but there is no way the child is mine.

I have a very unique last name, as in there are less than 5 of us in the USA, and it is fairly easy to spell. I have never tried to hide where I am at or where I am going so at any time she could have found me or had the courts find me. Today I got a message on Facebook Messenger stating that his younger brother wanted to know about me and that he wants to talk or connect. I simply closed this window did not reply and did not acknowledge that I even received it. The details matched exactly who it was that I was sleeping with and the location and timeframe line up as well.

I have since had a vasectomy and do not have children, but my main concern is with this being so far back could the state of Colorado significantly push for retroactive child support? It is my understanding that the husband was on the birth certificate and he has been acting as the father. Ever since I left I broke off all contact with them. This is 15 years and counting.

Obviously if the courts reach out I will of course comply with orders and retain Council but I just want to know if this is something I should seriously be concerned about. I currently live in Pennsylvania.