A grandparent of one's spouse.
My grandparent-in-law is a good person.
The great-great-grandparent of one's spouse.
My great-great-grandparent-in-law is a good person.
Spouse's great-great-grandparent.
My great-great-grandparent-in-law is a good person.
The great-grandparent of one's spouse.
My great-grandparent-in-law is a good person.
Spouse's step-great-grandparent.
step-great-grandparent-in-law.