2. refers to both husband and wife.

1: refers to a child.

4. Four old people (grandpa, grandma, grandma, grandpa)

2. Parents

1: children (only child)

There is no essential difference between the two answers. 42 1 means that both husband and wife are only children (so four have given birth to two children), and they have only one child, that is, 1, 42 1 reflects the family burden of the only-child couple under the one-child policy (if it is not the one-child policy, 4 not only gave birth to two children, but this 2 also lightens the burden.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.