Great-great-grandchild's child.
My great-great-great-grandchild is a good person.
Great-great-grandchild's child.
great-great-great-grandchild.
The spouse of one's great-great-grandchild.
My great-great-grandchild-in-law is a good person.
Great-great-grandchild's spouse.
My great-great-grandchild-in-law is a good person.
1- Stepgrandchild's child.
2- Grandchild's stepchild.
My step-great-grandchild is a good person.
1. The child of one's stepgrandchild.
2. The stepchild of one's grandchild.
My step-great-grandchild is a good person.