A couple said that when they had the first grandchild, it felt much different from when they had their own first child. It should be. I have to wait until I have my own grandchild to taste that feeling. Having grandchildren and great grandchildren must be one of the most joyful and grateful events on one's life journey. However, this life continuity from one generation to the next generation is not granted to everyone. Some couples don't have their own child. Some remain single for life. For them it is impossible to have their own grandchildren.
One of the interesting characters of God is that God does not have grandchildren. We believe and know that God can do everything. For the omnipotent God who can do all things, why does God have no grandchildren? Of course it does not limit God's omnipotence. It simply restrains God's almighty power by Himself to show us how much God loves each single person without any birth rank. At the same time it puts all humanity on the same rank and level to help people accept and treat one another in equality and justice regardless of who, what, how old and where they are. Truly it is God's unconditional loving action in fairness and justice for everyone and anyone.
In human perspective, there should be a certain order, rank, honour and respect in birth ranks among family as grandparents, parents, older and younger siblings and grandchildren. It also requires certain rules and regulations in the relationship with others such as in-law-relationships, relatives and friends in order to build up a mutual respect and keep each one's dignity. The truth is that these human relationships, even unique and special relationships such as husband and wife, grandparents and grandchildren and in-laws; all these could be changed and annulled when their relationship was done or irrelevant. But each one's relationship with God as a child of God shall never be changed. Why? Because everyone has to be someone's child. It is not necessary that everyone has to be someone's grandchild, partner, relative or friend but they must be an offspring of somebody.
I was once a grandchild of my grandparents. I scarcely remember them since they passed away when I was very young. Now I expect to be a grandparent someday. Truly time goes so fast! I feel that I am not young anymore. On the other hand, I give thanks to God who has made me as God's child; not to be a parent or to be a grandparent although I am and hope to be. Of course I am thankful for what I am now. The truth is that regardless of how old your children are, you feel that they are still your precious young children. Thus God loves the whole people as God's beloved children without any bias or exclusiveness depending on race, gender or age. Why, no grandchildren for God? Because God loves each single person so much that God could not leave them alone as other than God's child! Indeed it is God's love story for the people of the world.