Niko, the lovable reindeer is all excited and looking forward to celebrating Christmas with his family and friends. However, his plans take a sudden turn when he discovers that his mother Oona is getting remarried to a reindeer named Lenni. Adding to his woes, Niko also realizes that he has a new stepbrother named Jonni, who is smaller and younger than him.
Niko is not too thrilled about his mom's new relationship or the thought of having to share his family with someone new. To make matters worse, Oona and Lenni decide to go on a honeymoon, leaving Niko to take care of his little stepbrother Jonni.
Initially, Niko finds it hard to adjust to the new situation and take on the responsibility of looking after Jonni, who constantly gets into trouble. Despite his difficulties, Niko tries hard to bond with Jonni and be a good older brother. Their relationship takes a positive turn when they get lost in the snowy wilderness and have to work together to find their way back home.
As they journey back, Niko and Jonni get into various adventures, interact with several characters, and ultimately discover the true meaning of family. By the end of the movie, Niko learns to let go of his reservations and accept his new family, complete with his little, but totally adorable, stepbrother Jonni.