I [M] helped an infertile couple have 2 kids, and it was an amazing experience

This was about 5 years ago now… This couple whom I was friends with was trying to start a family. I knew the both of them from a past job. I wasn’t that close with them, but close enough to be someone they mentioned their struggles to. They kept trying for over a year and were having no luck.

They began exploring sperm donors, or even adoption. One day, it clicked in their head that I looked very similar to the father. Rather than going through all the hassle and costs of finding a sperm donor, they asked me if I would be willing. Looks-wise, this would make everything very easy for them and the rest of their family. Their plan was to just keep that a secret between the 3 of us and raise the child as their own (physically and biologically). I had no issue with any of it and was totally onboard. This idea circulated in their heads for months. At some point, I began to think it was a knee-jerk reaction on one of their parts, and unlikely to become a reality.