you can't go around mixing disease and magic ghosts! that's not a sentence!
if i remember correctly, it was the old woman who stabbed dio with the arrow, so maybe she also stabbed herself and her grandson before. maybe.
and the oingo boingo borthers, maybe they got stabbed too. we can't be sure they weren't.
and iggy, and that eagle, all got stabbed. and polanerref as wee kid, also got arrow stabbed. there was also dream monster baby, and invisible baby. maybe someone stabbed those babies with an arrow as well?
and wasn't there a pylon stand in the previous season? bet someone stabbed it as well!
I'm not saying that it's impossible, but in terms of story telling, it seems lazy. and if we say 'you can have a stand if someone in your family has a stand', we don't really need this entire thing. Some people have stands, and it runs in the family. the arrow is the exception to the rule, not the common thing. it's not supposed to be make sense, and trying to force the arrow stabs either makes it ridicoulous (as i tried to show above) or doesn't add anything to the table.

but about 'everybody gets stands', in the beginning of this season, we had the fat guy with the candle shadow stand that stabbed people to give them stands. it was supposed to stab whoever had the candle, and if they get stands, great, if not, kill them. how would that work?