From Bulbapedia, the community-driven Pokémon encyclopedia.
Shep is Lizabeth's grandfather. His only appearance was in Pokémon Ranger and the Temple of the Sea.
Shep is the only one of Lizabeth's family not to actually be in the acrobatic show their family puts on, although he plays a major, yet unknown role in planning it all out. He is much stronger than one might imagine, being able to row a whole canoe by himself. He has also traveled the whole world in his ship, The Blue Lagoon.
He only plays a minor role in the story, but does do things as help Lizabeth with the submarine.