Sara and Janne are married. They have no children together, but Sara has three children with three fathers. The children live with them and Janne is their stepdad.
The dads are all invited for Christmas, and their new wives, and their other children. Various people are each other's exes, several people hold various grudges, there are no two people you could pick out that have a healthy relationship.
This is the chaos the story *starts* at, and then it continually escalates. And 50% of the story is told in perfectly executed glances and body language.