Michael Ausiello of TV Guide had the following exclusive today:
[Marin Hinkle], the Two and a Half Men actress (she plays John Cryer's uptight ex) has been cast as Courtney McCallister, the bitter former spouse of Rob Lowe's Sen. McCallister, on Brothers & Sisters. She'll appear in one episode this fall, but it's likely she'll be back for more. In the episode, Courtney goes on a Larry King Live-type talk show to discuss her estranged hubby's bid for the White House — further inflaming tensions between the two.
This announcement deepens the Toobworld theory that 'Brothers & Sisters' is an alternate dimensional version of 'Jack & Bobby', [Thanks, Anonymous!] the series from a few years ago. In that show, Bobby McCallister grew up to marry his deceased older brother's girlfriend Courtney before finally becoming President.
Certain details are different, of course, which means that these two series are not in mirror universes. For one, Rob Lowe's version of McCallister in 'B&S' is a Senator from California rather than from Missouri as in 'J&B'. And the chronology is very much skewed since Bobby McCallister in 'J&B' is only about fifteen years old at most by now, and it's been a while since the former Brat Packer saw the edge of fifteen.
Finally, Senator McCallister's brother is very much alive, a minister, and gay. But these are the details which create divergent dimensions.