There is no relationship. The two of you do not share a common ancestor.
Your granddaughters and son have the relationship of nieces and uncle. Your granddaughters being his nieces and your son being their uncle.
In correspondence, you can address your granddaughter's husband as "Dear [His Name]" or "Dear Mr. [Last Name]," depending on your relationship and level of formality. If you have a close relationship, using his first name is perfectly acceptable. If you prefer a more formal approach, using "Mr." followed by his last name is appropriate.
You are not related as you do not share a common ancestor.
Husband and wife relationship is called a marriage.
granddaughter = nechda (נכדה)granddaughters = nechadot (נכדות)
My granddaughters and I are going to the store.
Hera had a very strained relationship with her husband.
Teresa Caltabiano, and two great granddaughters Lily and Emma
Your grandfather's cousin is your cousin twice removed. Her husband has no direct relationship to you.
The English language recognizes no relationship between you and your husband's great uncle.
Your sister's husband is your brother-in-law.
The Hebrew word for granddaughter is nechda - נכדה