The pasuk says about Yosef that he was Yaakov's Ben Zikunim. Literally this means the child born in his old age. Yet Targum Unkelus chooses to veer from the literal meaning and translates it as "Bar Chakim", his wise son. Why does Unkelus do this?
The Chinuch Malchusi explains that baby of the family usually gets the most love. The older children must endure the father's vision and his desire to raise the ideal child, the child of his dreams. When they fall short they pay the price and become a disappointment to their parents.
Not so the baby who is often treated more like a grandchild than a child, as he is overloaded with love and affection. Reality has set in, expectations are lowered, and age has softened the staff of the parents. The parents learn how to appreciate the good in the child, a thing that a well seasoned parent no longer takes for granted.
In this environment the child can flourish. His mind is at ease and his emotional needs satisfied. "Do not hit a child too much", says Rabbeinu Gershon (Bava Basra 21a). "No one ever got smarter from being beaten." With love you can do so much more!