A question can be asked, why was it necessary for the Torah to tell us that Yosef was able to see (or raise) his granchildren and great grandchildren? What's the lesson of the Torah? It seems to be superfluous?

The Torah is teaching us a very special lesson in the attribute of hope that each person should possess in the face of adversity....Yosef lived through many dire circumstances,namely

(1)hated by his brothers....

(2)sold into slavery

(3) living in an immoral society

(4) imprisoned in an Egyptian jail...........

Yet through all of this,was made viceroy of Egypt in addition to being able to witness the birth of his future generations.........

The lesson of Yosef is one of tremendous hope that no matter what ones circumstances are presently, it can all change for the better......Yosef knew that there was a purpose for his suffering, namely to be a conduit that in essence saved the world from hunger and famine.......Did yosef ever imagine while being in the pits of Egypt (jail) that he would eventually witness the birth of grandchildren???

A person must learn to trust in Hashem.......Shlomo Hamelach said it best in MISHLEI (19:21),"There are many thoughts in a mans heart;but the council of G-d shall prevail"........A person might imagine the worst, but eventually G-ds purpose will endure........