Dear Amy: My father died 20 years ago after a long battle with alcoholism. At the time, he was separated from my mother and estranged from my younger brother.

I chose to maintain a relationship with him through the last months of his life when he was suffering from liver failure, and I forgave him for the pain he had caused our family.

My brother did not maintain contact, and I completely understand why he made that decision.

At my father’s memorial service, a “mystery man” attended.

He didn’t come through the receiving line, speak to anyone in the family, bring a card, or sign the guest book.

Several of my relatives remarked later that they wondered who he was, but no one had talked to him.

He was well dressed and young — maybe early 20s (slightly younger than my brother and I), so not of the age that you would expect someone to show up at a funeral if they were not connected to the deceased.

At the time, family members made awkward jokes that I might have a brother I didn’t know about. It was an open secret that my father had affairs in the later years of his marriage, so there was the possibility that he had another child from an earlier relationship.

I have wondered about him ever since.

Part of me has always wanted to know, and as DNA tests have become more popular I’ve considered using testing to see if I have another sibling out there.

However, I’ve never done it, mostly because I worry about the impact that a discovery would have on my mother and my brother.