Bob and Fran have been married for 47 years. They have 3 children, 2 sons and 1 daughter, all ages being within 5 years of each other. Their 2 sons have 5 children between them. One son has 2 children. Their daughter has 3 children and 1 grandchild. If the son with 2 children had a grandchild, how many great-grandchildren would Bob and Fran have?

If a son were to have a grandchild, Bob and Fran would then have two great-grandchildren.

Step-by-step explanation:

C = children

G = grand children

GG = great grand children

Bob and Fran have 3 children, 2 sons (C) and 1 daughter (C).

Their 2 sons have 5 children (G) between them. One son has 2 children (G). Their daughter has 3 children (G) and 1 grandchild (GG).

If the son with 2 children had a grandchild (GG).

Now we can see that, at present we have a single great grand child that is of their daughter's.

As given, if a son were to have a grandchild, Bob and Fran would then have two great-grandchildren.