Eastenders - how are billy and bradley related?

[pattymc]

and Bianca and Max Branning?

But Zoe is Kat's daughter, so Pat would be her great-great aunt.

Pat was married to ian's dad before he married kathy

pat is max and Jack's stepmum???

no, that's Dot.
David Wicks is Bianca's dad, so Pat is her grandmother.
David Wicks dad is Pete Beale, Ian's dad, so Ian is her uncle.
Bianca's mum is Max and Jack's sister, Carol.