Garp seems to have half-white hair while Roger's hair was still black. Seems to be enough of an age difference that they aren't likely brothers or full brothers.![]()
I personally don't see much of a difference in their ages there, and since Roger died over 20 years ago, I doubt he'd look as young as Dragon does now and probably more like Garp. Rayleigh looked really young back when Roger was alive too but has a head full of grey hairs just like Garp does now.
Dragon has to be more than 34 though, assuming the youngest age he had Luffy was 16.

I'd like it if it was Ace the father 

