I just checked the Mario wiki. Most of the old sources refer to them as siblings, Mario and Sonic at the Olympic Winter Games refers to them as cousins, and most of the newer sources claim they aren't even related. It seems that their relationship is intentionally left ambiguous.
so if i was Mario i wouldn't talk to bowser, i would try to find a weapon like a gun and then shoot the toads and then make a trap to kill princess peach
