Isaac Spitzer

Malka/Molly's hot-headed, philanderer of a father who is also a gambler.

After losing his shirt-making business, Isaac becomes addicted to gambling, thinking he can recover what he's lost that way.

He keeps it a secret at first, but then, the gambling addiction gets increasingly worse. As he grows distant from his family, he finds refuge in flings and eventually takes on a mistress.

He gets along quite well with Ardalion (since they have...some things in common), Filippo (Frankie's father, who also has a gambling habit, although it's under control), and Harvey (Harvey gets along with everyone, it seems), and clashes with Pinchas and Lev.

In many ways, he's the opposite of both Pinchas and Lev - while Lev and Pinchas tend to be reserved and serious (with PInchas being dreamy and somewhat lazy while Lev is disciplined and determined), Isaac is emotional, unafraid to voice his opinions even if they hurt other people's feelings, and easily succumbs to "worldly" desires.

No wonder he gets along well with Ardalion. Ardalion is the tempter, while he is the temptee. Ardalion likes to stroke and inflame others' passions, while Isaac lives to inflame his own passions.