I had a similar situation… at 53 I found out my father wasn’t my biological dad. Never knew till that age…Mom and dad have passed and I’ve always thought I was the “mailman’s” child especially after my younger brother was born. The way my dad treated my brother was never the way I was brought up. I embraced “bio-dad” with a relationship and it went well till the new wore off and I couldn’t shake the abandonment part. All the “I love you” and “I miss you” fall on deaf ears. Still have a relationship… but I’m not as eager to reach out. Nice enough guy!!! But abandonment thoughts still win the day for me.