Jeb and Marco are both credibly rumored to have strayed from their marriage vows. In addition to financial murkiness and improprieties, this will give the Dems and the news media a lot of opposition research raw material to work with if either of them is the GOP nominee.
I’ve heard that Marco has a few financial deals that are very questionable.
Jeb made a career off his family name. He really hasn’t offered much else.