is he on this game and if so how do i unlock him ?

This thread has already been done. It's okay though, you didn't know.

quote G_O_G_E_T_A

In the Destined Rivals story, in chapter 03, go to the yellow dot at Kami's Lookout. King Kai will be there offering you a challenge, it will be against Grandpa Gohan. Beat him to get both Kid Goku and the fusion Potara called "Master Roshi's Pupil". This Potara is one of two needed to unlock Grandpa Gohan.

The other, Fox Mask, is located in both the Android and Buu saga's. In Android saga chapter 17, and Buu saga chapter 11. Go to the yellow dot at the Mountain Road, Yamcha will be there, beat him to get Fox Mask.

Note: this battle is very hard. I suggest you do it in Buu saga 11, because there you will have both Majin Buu and Hercule. In Android 17 you only have Hercule and that's not gonna work, I can tell you that. Be sure to power Buu up a bit with Evolution Z.

Once you have both Master Roshi's Pupil and Fox Mask, go to Evolution Z and fuse them. That will unlock Grandpa Gohan.