Jette Søndergaard and Peter Hansen Tygesen who play niece and uncle in the movie are in fact niece and uncle in real life.
The first line of dialogue in the movie is heard after 9 minutes, when the uncle says "Nutella" as he and Kris are out grocery shopping.
The director Frelle Petersen met the entire cast of Uncle (2019), during the production of Kunsten at græde i kor (2006), while working as assistant director. Kunsten at græde i kor (2006) was shot in the same area and same dialect as Uncle (2019).