I can't imagine that. My sister got pregnant when we were 15, it tore the family apart. For her whole pregnancy, she said she would put the baby up for adoption. She had the baby and decided to keep him. My mom mentioned that maybe she should raise the baby as her own and we would all be siblings instead of aunts and my sister the mom. I told her, hell no. That's not something a sane person does and I would tell the baby everyday who his real mom was and I would not keep the secret. She knew I meant it too. Thank God it never got to thatNo, not at all related. It's funny you mention that, as when they were little, they looked like they could be. When we were little (late 60s), the neighborhood kids used to say that I was adopted, and my brother and sister were the "real kids."
Remember, this is back when not many families adopted kids. And not many couples got divorced. My parents did. I told a friend that my parents were getting divorced, and she didn't even know what the word meant.
My best friend lived across the street. I found out 45 years later that she and her sister were adopted. They didn't know until their mother told them when she was ill and in hospice care. Can you imagine getting that dropped on you at age 55?