Is there a word for my relation to ex-wife's child?

If I marry a woman and she has a child, I am a step parent. But what if the sequence is reversed? For example, suppose I am married to a woman, get divorced and she subsequently has a child by someone else. Is there any word in the English language to describe what my relationship (if any) is to this child?

This is my situation; I'm close to this child and always at a loss to describe our situation as other than family friend. Can anyone offer another suggestion?

Solution 1:

"My ex-wife's child" is the proper description for your blood-or-marriage relationship with this child.

If you are back with your ex, you can call the child your step-child. If you adopt them, they are now your son/daughter.

Unlike "Significant other" (SO), there is no terminology yet to name this particular relationship that you can use and expect to be understood exactly.

Having said that, whose business is it that you would need to explain yourself so precisely? If he loves you like a father, and you love him like a son, and the mother goes along with this, describe him as your step-son. If someone questions you, politely steer the conversation the way you want it to go. "As I was saying, it was a great game. Have you been to any games lately?"