A Serpente (1992)

Two sisters are newly married; Guida to Paulo and Lígia to Décio. They spend their honeymoon in the apartment, a gift from the father of the brides. They will live there. Just a wall separating the intimacy of the two couples. Guida and Paulo are very happy. But on the other side of the wall; Ligia and Decius were never able to consummate their marriage. Decius is impotent and Ligia decides to commit suicide. To avoid the tragedy Guida, asks her own husband Paul to sleep with her sister for one night to help her losing her virginity. But when they continue to see each other, Guida gets jealous.

Unfortunately the movie A Serpente is not yet available on HBO Max.