I think that YA means that the relationships and dynamics you're discussing need to be seen through an adolescent viewpoint and not the more knowing lens of the adults.
This. And this again.
There's a lot of talk about age in YA, but I think that regardless of the age of the characters, secondary characters, etc., what makes it YA first and foremost is an adolescent POV.
Now, there are MGs and even some YAs with a omniscient narrator who is more than adult - ie, truly omniscient, like Death in
The Book Thief. But I think the
The Book Thief is more of an exception than a norm - and was not a debut novel. Markus Zusak had a strong following already, and the book had already been published in Australia (although there as an adult novel). Had Markus Zusak not been known as a YA powerhouse in the US, I'm not sure
The Book Thief would have been published as a YA.
But I think, generally, for a book to work in the YA market, the viewpoint needs to be an adolescent one. So...it will be somewhat tricky if you allow the father characters to drive the action OR show too much from their perspective (for my personal view of YA, I'd try to stay entirely in the adolescents' POV - ie, any actions or beliefs of the fathers is seen by the reader through the eyes and mind of the teen characters).
There are fantastic ways to drive tension and dramatic action by allowing the beliefs and actions of the adult characters to be revealed to the reader at the same time they are revealed to the teen characters.
If the lens of the omniscient narrator strays away from an adolescent POV it can really blur the lines on whether it is a YA or an adult novel. So, I'll never say never, because in publishing sometimes never been done before becomes brilliant - but there are few adult POV characters in YA, and even fewer from debut novelists.
But here's my final thought - why does it have to be YA? Why not write the book that is calling to you, and then see what the most marketable genre is? I think sometimes we can limit ourselves by trying to box in our ideas before they've even bloomed.
~suki