Just started a new campaign with the goal of getting as far as possible without cheating

Being in the beginning (271bc) I took over Taras first and got a message to move to the "rebelious" Rhegion.
Now, looking at Rhegion I see a general present as family member(!). I try diplomacy first because barging in when someone is family....well, you know...

Okay my question is: does anyone know how to handle this correct?
Should I lay siege just like that or threaten the settlement or can he be bribed at the right circumstances?
(I expect something like that because it's family)


Thanx