He is your Grandfather, and is your son's Great-Grandfather.
You can't have a grandfather 5 times removed. You could have a 5Great grandfather. In which case the relationship would be your 3Great Grandfather.
Your Grandfather or your Great Uncle.
your son is your great grandsons grandfather.
It could be your grandfather. Or it would be a great uncle.
Your grandfather's brother's daughter is a 1st cousin of one of your parents. Her son is your 2nd cousin.
my sexual partner
Great great grandfather
Your daughter's son is your grandson and you are his grandparent.
If you are a male, you are the grandfather, and if you are a female, you are the grandmother of your daughter's son. In other words, you are his grandparent and he is your grandson.
I'm not sure who Roger is, but yes, the relationship is quite possible. Roger's grandfather's son could be Roger's father; His daughter's grandfather could also be his father, one and the same person. lol
The relationship to the grandfather or the relationship to the grandson of the grandfather? Let's say your name is Ken, your grandfather's name is William, his brother's name is Eli, and Eli's son is named John. If you're asking about William and John's relationship, they are first cousins. If you're asking about Ken and John's relationship, they are first cousins once-removed.
Your grandfather's sister's children are your 'first cousins once removed'.