"Imcompreso" aka "Misunderstood" (1967)
From IMDb review:
A consul's wife dies, and he's left on his own with his two children. He's a good father, but he wants his older son to become adult, to act like a man. ... In many a melodrama, we have heard the mother say after the father's death, "Now you're the man". Comencini's work is the contrary: for him, even if a child shows more perceptiveness than the grownups, he still remains a child who should be allowed to suffer, to cry and to love. Because the father thinks that a big boy does not need tenderness anymore, he takes only the little brother in his arms.
The mother is still here even if the boy does not see her anymore. There's a painting in the house, a tape which the father recorded before her death, and mainly a big garden where the two brothers speak of intimate things like death. All the nannies in the world that the wealthy dad can pay cannot. ... The first part of the film tends to show that Milo, the little kid, is the frail one ...