Somebody Else's Children (1958)

Nato, a student, befriends two children in the street, a brother and a sister. She does not know that their father just broke up with his wife on the grounds that she was not able to find a common language with the children. Once he meets with Nato they fall in love, but their relationship does not last long because one day he meets his estranged wife by chance and goes off to be with her, abandoning both Nato and the children. Desperately Nato wants to take off, too, but realizes she can not leave the children alone.

Unfortunately the movie Somebody Else's Children is not yet available on HBO Max.