Okay so, I have like five different headcanons and universes, but this is my “main” about the Deuteronomy family that does at least somewhat work with “canon” cats
So. Deuteronomy and Grizabella were mates but with a very open relationship. Macavity is the oldest child, but Griz is not his mother. Idk who is but I don’t think it’s anyone in the junkyard.
Deut and Griz are Munkustrap’s parents, and Munk is a little younger than Mac and thus had to spend a lot of time with his older brother (it wasn’t pleasant time).
Griz is the mother of Demeter but Deut is not the father, the father is unknown. Tugger’s father is Deut but Griz is not the mother, once again idk who the mother is. Might be someone in the junkyard this time. Tugger and Demeter are close in age and despite not being actually related they see each other as siblings. Tugger kinda sees Macavity as his brother, but Demeter does not (both because she isn’t related to him but also because he was barely present and he left shortly after her birth).
The role of being a protector was originally intended for Macavity, since he was the best fighter/the most interested in fighting, and he was gradually trained to this. Munkustrap was more interested in storytelling and that was what he was going to be, until Mac suddenly left and they passed the protector training onto Munk. This kinda failed for several reasons, because a) his training was a lot more stressed than it should have been and he never properly learned to take time for himself/how to prioritize/ask other cats for help but instead felt he had to do everything himself b) everyone was upset by Griz and Mac abandoning them, meaning Deut was pretty absent during this time and didn’t properly check up on his son + probably a lot of other things (like no one actually making sure this is what Munk wants) but yeah.
And then not too long after, a teenage Demeter starts a relationship with Mac and leaves the junkyard, being gone for like, a year or two.
Deuteronomy never really treated his children as his children, but rather like any members of the tribe. While he obviously loved them, he wasn’t really a father, and Grizabella didn’t care much about her family and was too busy with herself to be a mother, meaning both Mac and Munk essentially grew up without parents. Tugger and Demeter, while not having Deut as a father, at least had Munk who basically became a mix of older brother/father to them and especially Tugger wasn’t really affected by Grizabella leaving. So all in all, Tugger and Demeter had a decent childhood, at least compared to their older brothers.
There’s a lot more but this is what I currently had in mind. This was written on my phone without any kind of proof reading so I apologise if it doesn’t make much sense