Jeff Daniels will join Jon Heder and Diane Keaton in “Mama’s Boy,” the Warner Independent Pictures comedy that will be directed by Tim Hamilton. Hank Nelken wrote the script.Heder plays a slacker who must re-evaluate his life after his mom, with whom he lives, gets a new boyfriend, a self-help guru. Daniels will play the suitor, who begins to edge the youth out of the house, prompting a mano-a-mano confrontation. Heidi Santelli is producing and Steve Carr is exec producing. Daniels, who’s coming off “The Squid and the Whale,” has been shooting the Scott Frank-directed “The Lookout” for Miramax and Spyglass.