Excel 365 Getting a Drop down with right Parent for Child

Question

I have a family tree with 4 generations. I have put them into named groups of Parent and Child, for a child in 1st generation becomes a Parent in 2nd generation and so forth.

I can easily, pending some rules, decide what Parent resides in 1st generation and a list of Children from Parent.

When you work with this for a while you start to recognise a system of Children in the 4th generation, and you then just select that Child and from that choise I can then select (XLOOKUP, VLOOKUP) who is the Parent of selected Child.

My problem comes when my children Peter, Joe, Beatrice, Jim, Joe suddenly gets an overlap. The 2 Joes which normally have 2 different parents now only have 1, due to LOOKUP only finding the first solution.

I can easily make a FILTER of which Parents are linked to a Child, and list them seperately but I need that FILTER inside a Data Validation (Drop Down). I have tried the INDIRECT solution and it didn't work as intended. FILTER(Parent;Child=D5)

The function I'm using right now is XLOOKUP(D1;Child;Parent;"not found";0;1) , that works brilliantly when the family tree is straight up and clear. I select the Child, it finds the Parent, which in turn find the (Grand)Parent, etc. When I do find a Joe it returns the Parent of the 1st Joe in the system, messing up the family trees.

Optimally I would have a Drop Down of the possible Parents of this Joe and then the family tree would continue.

(There's a client and level of IP involved. The specific word is 'Other' and several trees are using the word to describe a group of products. Due to IP I can't change any names or make it Joe 1, Joe 2, etc)

I have 1000s of rows of this, when I've selected a family/product-line for a row that row is done. I can't feasible allocate that Drop Down out. The filter needs to be incl in the Drop Down/Data validation menu. Each time the client returns with a new Workbook, I'd prefer I just copy-paste the logic and easily covering the 1000s of rows.

4 generations and 5 families. If for each generation there'd be a drop down of Parents for a Child, that would solve for those families with a Joe.