I thought a secret child of my husband's had turned up once. I opened the door to this young man, he was similar height to my husband, around 6ft, he had black hair like my husband, he was slim like my husband and whilst my husband is clearly mixed race this young man had a slightly tanned looked to his skin, in fact he was probably a bit darker than my kids but his features weren't like my husbands/my kids.
It was a bit awkward as I had a friend there.
The young man asked for my husband by name, I said I'd find him what was it about and the young man said it was personal. I went and got my husband, he went to the door, came straight back in looking a bit shaken, grabbed his coat and said he was going out.
It turned out it was the child of an ex, he remembered my husband fondly and wanted to come and tell him that his life had worked out well, he was getting married and his future wife was expecting their first baby.
My husband was so pleased he remembered, he was about 5 when my husband knew him and bought him toys and played soldiers with him but never saw him again when he split with the GF.
I really thought he was going to come back in and say that this was the son he knew nothing about. My friend was agog.