Your son and grandson may be father and son, or they may be uncle and nephew.
The son of your grandson is your great grandson. You are his great grandmother or great grandfather.
Your daughter's son is your grandson and you are his grandma or grandpa.
If your daughter-in-law's grandson is a child from a marriage before she married your son, or after their marriage ended, her grandson is not related to you. If he is a child of the marriage between your son and your daughter-in-law, then he is your great grandson.
Your grandmother's sister is your great aunt. Her son's daughter's son is her great grandson. You and your great aunt's great grandson are second cousins, once removed.
Your grandson and great grand son could be cousins,(first cousins once removed), they could be uncle and nephew, or they could be father and son. It depends on how they are related to your children. If your great grandson is the grandchild on one of your children and your grandson is the child of a different one of your children, they are first cousins, once removed. If your great grandson is the child of a sibling of your grandson, then they are uncle and nephew. But your great grandson could also be the son of your grandson. Then they are father and son
Your grandson.
A person's son's son would be their grandson. Your son's daughter would be your granddaughter. Your grandson's son would be your great grandson.
A person's son's son would be their grandson. Your son's daughter would be your granddaughter. Your grandson's son would be your great grandson.
The sons of your son-in-law's siblings are his nephews. You are not related to them.However, your son-in-law is married to your daughter. The sons of her siblings are also your son-in-law's nephews. They are your grandsons.
Your granddaughter and your niece's son (the grandson of one of your siblings) are second cousins to each other.
The son of a father's son is commonly referred to as a grandson.
Bob is the grandfather and Tom is his grandson.