We have two women friends (unrelated) and each woman found an unknown half sister, close to a decade ago.
Not only are they now close to their new sisters, but their new families.
My wife had an uncle (one of 8), who just disappeared and left his family in his hometown. They thought that he was dead.
Years later his daughter via a second unknown marriage to the original family surfaced after her dad, the missing uncle died living 100 miles from his first family and his brothers.
She made contact with my wife’s dad and another one of his brothers, her Uncles. She later said that her son couldn’t handle knowing what his Dad did. So, she asked them not to contact her any more. Her and his loss.
Another man we know with 3 siblings, found our his mother was a real love child as he and the other 3 siblings had 4 different Dads. I think that there were 11 unknown siblings due to the wandering Dads and the love child.
He said that Christmas’s were interesting and you needed an IPad with DNA trees to keep track of everyone.
A non family member at one of these Christmas parties, asked one of his newer sisters how they were related,
She replied, “By intercourse!” Now everyone in that really extended California family uses that relationship term.
That is funny, related “by intercourse!”.
At least in our situation, we are all old enough to be somewhat understanding of transgressions, accepting of reality, etc.
But, for example, the new half-sibling has two children, who would now likely find out that their adored grandfather wasn’t really related to them, and their adored grandmother may have cheated on him, which might be hard for these young adults to take in.