Sommertage (1990)

Micha is 16, a difficult age. Like every year, he spends the summer holidays with his mother and brothers in a country house in Sweden. When the mother goes to Stockholm for a week, Isabelle, the fun-loving daughter of a friend, looks after the children. Micha lives under Isabelle's care, feels taken seriously for the first time and treated as a "man".

Unfortunately the movie Sommertage is not yet available on HBO Max.