A Summer in the Mountains (2011)

Hamburg boy Leo Vandenbroek is not amused when his mother, ER surgeon Pia, drags him to a godforsaken Bavarian village for her 'long overdue relaxing holiday'. In fact she rented from local doctor Peter Huber because he's married to Maria, who she learned in her recently deceased father's testament to be her illegitimate half-sister. Leo, who misses his daddy since Pia's career ruined her marriage, instantly bonds with Peter, and ultimately even becomes the glue to reconcile him with his father Karl, who is embittered since his wife's fatal disease.

Unfortunately the movie A Summer in the Mountains is not yet available on HBO Max.