After being tossed out of med school, 21-year-old Josh returns home and finds out that Riley, the young boyfriend of his mom, Fran, is living with Fran and his sister Allison, and that a guy named Duane is living out of his closet. Now Josh must be convinced that he can adjust to this bizarre new arrangement.
Riley's parents come in for a visit and get quite a surprise when they learn how old his girlfriend is. During an attempt to get his mother to warm to Fran, Riley accidentally cuts his finger and is rushed to the hospital, at which time Fran eases the mood by telling Riley's parents about how the two met.
In the midst of planning a family getaway, Fran's ex-husband Ted comes back into the fold after a long absence and wants to reunite with the family. After trying to mend ways with Josh, buying Allison presents, and tempting Riley with a job, an annoyed Fran realizes Ted is just trying to control of the situation. Meanwhile, Josh accepts a job as a video store clerk.
As Riley's high school reunion approaches, Fran has concerns about how she'll look to his friends, which get turned around when they attend and it turns out that all his friends' wives are the ones fawning over her. Riley must soon change his old classmates' opinion of the relationship, however, when he realizes they think Fran is his "sugar mama."
When Fran starts a family album that could kick off the newly-minted relationship with Riley, he stuns her by telling her his wish to someday put in pictures of their children. Feeling somewhat worthless, Fran must also convince a somewhat doubtful Josh that she was thrilled to be pregnant with him. Meanwhile, Ryan's parenting skills are put to the test when he assists Allison with boy troubles.
Josh and Riley begin to get suspicious instincts about Allison's new boyfriend, Kurt, causing Fran to rethink the level of trust she has in Allison's ability to handle her love life decisionmaking. Meanwhile, Josh and Riley are shocked to find themselves in sync over this issue.
Fran decides to organize the plans for her first Valentine's Day with Riley after not liking the plans he initially had in store for the two of them, which makes Riley feel as though he has no say in the relationship. Meanwhile, Fran tries to help Josh's new girlfriend win him over, unaware of his desire to end the relationship, and also gives ill-fated advice to Allison about tracking down her secret admirer.