My Great Aunt's dad is my Great-Grandpa

not my great uncle. So if i were the mom, my Aunt's dad is my Grandpa, not my uncle. my aunt's husband is my uncle, by marriage. if my aunt is by marriage, then her dad is nothing to me. So wouldn't the mom have known her aunt's dad was her grandpa even if the kids were too dopey to know their great-aunt's dad was their great-grandpa? is this sloppy Hollywood writing, or do they figure this out in a sequel?

Ask a fish head anything you want to, they won't answer. They can't talk.