I've name changed for this post.
Me and DP are in our 20s, a few months ago his ‘cousin’ told him that their brothers and that they have the same dad (his dad passed away a few years ago so DP couldn't ask him either). DP brushed it off and didn't really have any proof, he just thought he had jumped to that conclusion when he thought the family didn't care about his dads death. He kept saying it and he told DP why he thought it and DP started to believe him.
DP asked his mum and she denied it, he then said that he'd do a DNA test then and she admitted it. He then found out that everyone knew including the man who thought was his dad.
DP was understandably very angry and decided to not talk to them for a while. His family then started blaming his half brother and called him spiteful for telling DP the family secret.
DP still doesn't want to talk to them but his mum has called him ‘selfish’ as his sister (11) misses him, even though his mum stopped them from contacting each other until DP starts talking to them!
DP still doesn't know what he wants to do yet but he's still angry for being lied to.