A newly blended family and two polar opposite stepsiblings named Erin and Aaron who come together through music.
Erin and Aaron's first day as step siblings and they are in no mood to get along. But when they discover that their differences may lead to a family break-up, they must find a way to come together.
Aaron finds the perfect replacement for his beloved broken piano but the shop owner, Mr. Ledder, has a history with Erin and refuses to sell the piano to an instrument killer like her.
Aaron sets out to find a girlfriend to break his heart so he can write a hit song, that girlfriend turns out to be Erin's BFF, Vivian; Erin tries tricking Vivian into breaking up with Aaron but ends up betraying her trust.
Erin and Aaron clash over Saturday night traditions: Erin wants pizza and Aaron wants sushi; Chuck and Natasha have a special daddy-daughter day planned but struggle to find a shared activity they'll both enjoy.
While Chuck and Sylvia take a vacation, Erin and Aaron convince their parents to let them babysit Natasha, not realizing how much trouble she will be.
Erin and Aaron are excited to compete in the music competition between band and chorus with the winning team getting a trip to New York City; Erin's laid-back ways causes Aaron to kick her out of band, driving her to battle it out by joining chorus.
Erin and Aaron decide to have a sing-off to see which one of them gets to keep their first name; when Aaron loses, Erin pushes him to adopt a new country persona to match his middle name.
Erin invites Aaron's old friends and teammates, the Yellow Jackets, to visit him, not realizing Aaron never told them about his love for music; when Aaron lies to his friends, Erin has to convince him to come clean.
After Aaron urges Erin to bond with Sylvia, Erin and Sylvia start spending lots of time together making Aaron and Chuck feel left out; Natasha tries to gain power at her school by having Vivian and Hunter impersonate Erin and Aaron.
When Natasha plans an elaborate photoshoot for the family's moving announcement, Erin and Aaron fear the pictures will be a social disaster; Sylvia and Chuck lose Captain Cutie Pie and go to great lengths to win her back.
While Erin struggles to get a date with her crush, Cayden, Aaron has money trouble for a date with his crush, Lily, at an expensive restaurant; Erin and Aaron decide to be in cahoots and come up with the ultimate plan to land them their dates.
When Erin and Aaron upload their songs online to choose which one to perform together at Asbury Park's "Porchfest", a Grammy-winning producer reaches out with a life-changing offer for one of them.
With Erin in New York, Aaron is forced to play Porchfest solo. But Aaron can't write songs without Erin, and Erin only wants to perform with Aaron.
