Coincidence or Genes?

A wealthy couple adopted my paternal grandmother in the late 1930s. I never thought to question this, as it seemed a rather straightforward narrative. However, this may not be the case. By way of accidental sleuthing, I noticed that Grammies 'adopted' father looked strikingly similar to her. They had the same face shape, the same smile, and positively identical eyes. I said so as I examined a picture of this man who died years before I was born. My father heard me and made the sort of face he often did when he didn't want to admit something. He told me later that it was likely the man in this photograph was Grammies biological father. From what could be discerned, this man had an affair, the woman got pregnant out of wedlock, and to hush everything up, my grandmother would be explained away as an adopted child. I was shocked to learn every bit of this (potential) story, and more so when, years later, a friend tried to trace her own grandmother's story, and it turned out she had been adopted under similar and equally scandalous circumstances. Both grandmothers passed away long before DNA kits and like became the norm, so unless quite a bit of time and money is invested, the truth may remain in the 30s.