My family is eastern European and before he met my grandmother and had my dad, during the second world war my grandfather had a romance and baby with a very cool Jewish lady (but because of his army affiliations, could not easily be with the mother of the child in that political climate.... Which is heartbreaking).

the child's mother put the son in an orphanage to keep him safe during the war. My dad lived until his sixties thinking he was an only child, and his father passed away before we could find out whether he ever knew about the child. the half brother had been a poet/artist in Europe but died before we found out about my dads connection, but it seems he never knew who his father was. His daughter reached out to us after doing ancestry research (we confirmed with a dna test) and her daughter is almost identical to my sister and theyre very, very sweet and my sister met her in California a few years ago :)