What is the probability of having twins if your dad is a fraternal twin and you are a identical twin and your moms dad is a fraternal twin?

The probability is the same as if you had no history of twins in your family. There is no genetic component with identical twins, it is just something that happens. Fraternal twins occur if a mother "drops" two eggs in one month. Your father being a fraternal twin does not make you "drop" more than one egg in a month and so does not increase your chances of having twins. Your maternal grandfather being a fraternal twin did not effect your mother's ability to drop more than one egg and so did not effect your ability to "drop" more than one egg and so does not increase your ability to have twins.