It's been announced that Rob Lowe will be joining the cast of 'Brothers & Sisters' on ABC for at least six shows. Jon Robin Baitz wrote the part of a McCain-styled Republican senator (more moderate than jerk, I guess) with Lowe in mind, and he hopes the actor will stay on after the six episode arc is completed.
This senator will appear as a guest on Kitty Walker's TV show and will eventually become one of her "suitors".
As most politicians always seem to have some kind of political scandal in their backgrounds, it's always possible that this senator has an identical half-brother residing in Washington, DC, by the name of Jack Turner.
But neither one of them would be related to Sam Seaborn, even though his father was a known philanderer.
This is, of course, because Sam Seaborn resides in an alternate TV dimension in which Jed Bartlet was the president of the United States instead of Bill Clinton and George W. Bush. (And before Bartlet, Owen Lassiter was the POTUS.)
'Brothers & Sisters'
'The West Wing'
'The Lyons' Den'