What’s the name for Gary and Harry’s blood relationship?

Imagine that Gary and Harry are these two guys in a hypothetical family, described in English below and in this diagram represented by the green cells at the bottom:

As you see, Gary and Harry are related to each other by blood, so one is the other’s something or other. What I want to know here is what that something is. That way Gary could tell someone that “his _______ Harry stopped by the other day”, or vice versa.

In other words, is there a word — or words — that fit these two blanks?

• Gary is Harry’s ________.
• Harry is Gary’s ________.

This might be the same something, like with cousins, or it might be different somethings, like uncle and nephew.

Here’s their family tree, which starts with two couples, Andy and Betty on one hand and Charlie and Daisy on the other, in which none of the four is related to any other of the four by blood, only by marriage alone.

1. Andy and Betty marry and have a son Eddie.
2. Charlie and Daisy marry and have a daughter Fanny.
3. Later, Andy divorces Betty and marries Charlie and Daisy’s daughter Fanny, and then Andy and Fanny have a son Gary together.
4. Also later, Daisy divorces Charlie and marries Andy and Betty’s son Eddie, and then Daisy and Eddie have a son Harry together.

That means that Gary is Andy’s son and Daisy’s grandson, while Harry is Daisy’s son and Andy’s grandson. Gary’s half-brother Eddie is Harry’s father, while Harry’s half-sister Fanny is Gary’s mother.

Given that Andy is Gary’s father and Harry’s grandfather, and Daisy is Harry’s mother and Gary’s grandmother, Gary and Harry are definitely related to each other — but how?

• Gary is Harry’s ________.
• Harry is Gary’s ________.

While I realize that not all extended, by-marriage family relationships have a name for them in English that do have a word for them in other cultures, that’s not what I’m talking about here. These are for people who actually share blood with each other, so you would think some combination of cousin or uncle or nephew or grandson would work here.

But what?

Here’s that diagram again in case in helps to see it closer to the English description.

_{This idea and original diagram from F.M. Lancaster’s Genetic and Quantitative Aspects of Genealogy: Types of Collateral Relationships}

Solution 1:

You'd talk about the father's side and mother's side separately. (Credit @JoshRagem's half-uncle / half-nephew idea.)

Consider Gary.

• Father's side: trace the relationship through Andy. Harry is the son of Gary's half-brother. So Harry is Gary's (half-) nephew on his (Gary's) father's side.

• Mother's side: trace the relationship through Fanny. Harry is Fanny's half-brother. So Harry is Gary's (half-)uncle on his mother's side.

An uncle is the brother, half-brother, step-brother, or brother-in-law of one's parent, or the husband of one's aunt. - wikipedia

So Harry is Gary's paternal (half-)nephew on his father's side and (half-)uncle on his mother's side.

Correspondingly, Gary is Harry's (half-)nephew on his mother's side and (half-)uncle on his father's side.

Solution 2:

Based on some comments of the question itself, I'm going to pose this as a possible answer.

Purely on the final result of the "family tree" we have the following analysis:

• Gary's mother is Fanny and Fanny's mother is Daisy. This makes Daisy Gary's grandmother.
• Daisy's son is Harry.
• This makes Harry Gary's uncle.

The same relationship can be given if analyzed from Harry's perspective:

• Harry's father is Eddie and Eddie's father is Andy. This makes Andy Harry's grandfather.
• Andy's son is Gary.
• This makes Gary Harry's uncle.

So, Gary is Harry's uncle and Harry is Gary's uncle. This makes them both each other's uncle.

Transitively, this also makes them each other's nephew.

In incestuous relationships, one person can be labelled with two different relationships to somebody. For instance, where a mother and son produce a daughter, the mother is both mother and grandmother to the daughter.

In this question, there is nothing incestuous happening. However, because of the divorces and marriages, it has the same kind of sense.

The divorces and marriages may or may not cause some additional confusion. In my analysis above, I only traced each person's genealogy through a single parent relationship.

I'm not completely certain if this makes them half-uncles (and half-nephews) or not.

It's also possible that there are some additional half- or step- terms that could be used. But my brain holds up a white flag at this point and won't keep going . . .