The film is a reconciliation tale that focuses on a man (Timberlake) who is trying to reconcile with his former sports pro father (Bridges) as they head to his ailing mother's bedside. As Christopher Campbell noted back in April of 2007, there's also a girlfriend in the road trip mix. THR says that Kate Mara is the other player in this film, so I imagine she's Justin's love interest. As for Lyle and Harry -- the former plays a Memphis bartender who "lends a helpful ear" to Timberlake's character, while the latter will play his grandfather.
After his creepy stint as Roman Grant in Big Love, it will be nice to see him as a grandfather who isn't some gangster-like Mormon. Then again, maybe he is, but that'd be a totally different sort of story. Production is currently underway in Louisiana.