My wife did a DNA test and got an inquiry from a close DNA cousin according to test results. That person says she was the product of an affair her mother had with a man who later died in the Korean War and she wanted to know more about her biological father. She gave the few details she knew. My wife recognized a few of them and thought it might have been one of her uncles, but he was never in the Korean war. My wife contacted one of her uncles daughters, explained the situation and asked her if she would like to contact the person to find out more.
Well it turns out that the tow half sisters met and have communicated regularly with each other. They were both old enough and mature enough not to be angry at the man who cheated and fathered both of them.
Infidelity is not as uncommon as most folks think, especially in populated areas. DNA, along with sperm donors helping couples get pregnant is complicating DNA genealogy. And then lets not get into the complications caused by bone marrow donors and certain organ donors is confusing DNA genealogy.
Then again, there is the ugly side. Some babies are adopted because of rape, poverty, drug addiction, abuse, etc. Often they try to keep their historic origins a secret and sometimes their adopted parents keep it a secret from them. So they can be really surprised when their children get DNA tested and find out they have lots of close relatives they never heard of.
You will never likely know what really happened. It is best to just accept it and find out about your new family tree branch.
Good luck.
Thank you for your thoughtful advice and sharing your wife’s experience.