1 Shakespeare: So, if my grandfather is dead before my mother was conceived, how am I still here?
2 Mercutio: I guess the time travel has created an alternative timeline.
3 Mercutio: We haven’t actually changed your past, we’ve just erased the Will who would have existed in this timeline.
4 Shakespeare: That can’t exactly be good.

One potential solution to this problem is for Will to go find his grandmother and - ahem - become his own grandfather. But as this is a family-oriented comic, we won't go there.

Also, that's just silly, and obviously leads to even more problems.

Hmmm... on second thought...