Not sure if this is the right group. I need some input on this crazy hodgepodge mess. Have any of you discovered you have half siblings as an adult?

Background: about 10 years ago I tracked down my mom's ex husband, looking for details on medical history. He told me I wasn't his biological child, he adopted me shortly after marriage (I was 4ish). I confronted my mother and she refused to tell me who my bio father was.

About 3 years ago my half sister (same age) tracked me down through my godfather. He convinced my mother to relay my sister's details. So apparently I have 3 half siblings. They have known about me their entire lives, but I didn't know about them.

Today the eldest sister reached out to me. They both remember seeing me when I was about 8, but I have no memory of them... This bothers me

My mother has her reasons keeping this secret. She feared bio father, and hated a court ordered visatation. Talking to my half sisters, it really messed with them suddenly losing a sister and not being allowed to talk about me (their mom hated my mom). Knowing I occasionally played with them until I was about 8 is unsettling, I should have some memories of them. I wonder if my mom essentially gaslit me. My mom won't talk to me about this.