Just a theory I've been thinking about.
If you are the first child are you closer to your df and if second are you closer to your mum? (Sorry, haven't thought as far as third and beyond but would be interested to know!)
I don't mean which parent you love more if that's the case. Just which one you're closer to.
I am a second child and was closer to my dm growing up but not for any reason I can think of as I love my df dearly. My older sister had a very close relationship with my dad.