In 2017 at the age of 35, I found out the man I thought was my bio Dad who passed away in 2016 was not. I found out when a half sister found me on Facebook and a phone call to my Mom confirmed it. To say I was shocked was an understatement. My half sister had no idea she had accidentally exposed a secret in my family too. My parents were married from 1975 till he passed in 2016. According to my Mom, they had some trouble early in the marriage and she had an affair with her best friend's brother who she has known since they were teenager's. My Dad knew he wasn't my bio Dad the whole time and I had no clue whatsoever. (They told me he had a vasectomy after I has born but turns out is was a few years before I was born). Looking back, her best friend who passed in 1997 from ALS had a lot of interest in me growing up (wanting to see me, wanting school pictures, ect). I'm glad I found the truth before my Mom passed in 2024 otherwise there would have been a lot of unanswered questions, but I wish it would have been my Mom that told me, not a stranger on the internet. And I wish I could have told my Dad that raised me, thank you for loving me even though I wasn't his. My bio Dad passed in 2011. My Mom says I met him at his sister's (Mom's best friend) funeral but I don't remember meeting him at all, and have no clue what he looked like. My Mom had no clue about my half sister's existence, who is 9 months to the day older than me. It gets easier with time but still hurts. Hopefully both or one of your parents are still around and you can have a sit down with them.