Dear Abby: I found my biological father 3 years ago but feel awkward on Father’s Day

Dear Abby: Three years ago, I found out that the man who raised me wasn’t my biological father. I suspected it for many years and asked my mother about it twice. She angrily denied it both times. The man who raised me was definitely my dad. He passed away in 1989. I recently found out that he knew of my parentage all my life.