A great-grandparent or great-grandchild.

plural of great-grand

(medicine) Having ten or more pregnancies, resulting in viable offspring.

(medicine) One who is great grand multiparous.

(medicine) The condition of being great grand multiparous.

plural of great grand multipara

The daughter of someone's grandchild.

The mother of one's grandparent.

The father of a grandparent.

A son of a grandchild.