omg i love it. he could be a cousin from the father's side but they're from italy, the mother is american but tbh idk if the family that brought me in is even still active so if they're not i might change rex's background to be british (i love tom hardy's accent lol) all this to say you can have flexibility about his background? like if you wanted to keep jrm's irish roots, it could be like rex's aunt's husband who's irish and he grew up there