The moment Jack got the call, he felt something inside him snap. Last nerve? Try a tenth of his last nerve.
The one thing Jack Bauer held most dear, especially after the horror of the 2001 primary, was his family. His wife was dead. His daughter estranged. So of course his father -- a man he hadn't spoken to in nine years, ditto for his brother and Graham's family -- had to come up in the course of the investigation.
And of course, they couldn't find his father.
That meant the only reliable source of information he had was his estranged brother. A man that Jack had never really liked all that much.
He didn't want to bring his family into this or anything else. There was a reason that he had gone on with his life, without them. The only one he ever really trusted was his sister, Carol. He had cut himself off from the rest of them, nine years earlier, when he'd joined CTU. And even his relationship with Carol had struggled with as incredibly distant as Jack had become.
That, and anyone who knew him well enough would be able to see this and have a big 'oh shit' siren go off in the back of their heads. They'd be trying to keep him from doing something stupid.
He can see the looks on Mark's and Jordan's faces right now. Especially Mark, because he knows that Mark is watching him like a hawk, worried about him. It's good to have someone who worries about him, because no one in his family does.
Jack knows he should tell them. He trusts them. But he doesn't want them involved in his family business. He doesn't want to show them how incredibly fucked-up his own upbringing was. There's an amount of pride.
Instead, he drops the other agent off and drives.
He'll tell them later.