I'll run through this by part ( Sorry if I use the term Jobro wrong. Ik some people use it in different ways but I just use it to describe a main ally to the Joestar bloodline)

Jonathan: Jonathan was surrounded by a lot more well trained hamon users, including Strazio, Tonpetty,.and Zeppeli.

Joseph: While he is is exceptionally crafty and just pulls the most random bullshit out of his ass. Lisa Lisa is a much more skilled hamon user and fighter having years apon years of actual training and practice under her belt. The only time we did see them fight Joseph got humiliated, granted he was weaker than but I think the results wouldn't change much.

Jotaro: This one may be a bit controversial however I believe up until the end of p3 Avdol was actually stronger with Jotaro. Without time stop Avdol would actually stand a pretty good chance against Star Platinum. Having much better range, arguably the same strength, and we already know it does well against quick closer range stands because of the fight with Polnareff.

Josuke: While I originally wanted to put Jotaro I decided not to because he is an actual Jojo. So I ended up going with Rohan. This is just because of Heaven's Door, better range and much more broken ability.

Giorno: This one is another debatable one, but I ended up choosing Fugo to be stronger than Giorno before he got GER. Fugo is more experienced with his stand in an actual offensive way. And arguably Purple Haze is definitely the more deadly and better for combat stand. Another one you could maybe argue is Mista but like I said debatable.

Jolyne: She's the easiest to say who's stronger than her. Jotaro and Star Platinum are technically part of the part 6 group. But once again Jojo not Jobro. So I decided to go with Weather Report, because yeah Weather Report the Stand is just that broken with it's weather abilities. Anasui is another one you could probably argue.

Fun fact, all the original universe JoJo's have a Jobro stronger than them.