User blog comment:Ghmorello/Chapter 887: Hot Pounding/@comment-24769684-20171201073703/@comment-24850639-20171204172507

^ Personally I believe Oda was hinting at Pez having an early onset of Observation Haki. Remember how Aisa displayed properties of it as well as a baby, crying whenever there was conflict of some kind, but also being joyous and happy when all was well in the village? I think Pez felt the love of his grandfather being able to see him, and at the same time immediately knew when his life was in danger.

Your question still stands, in terms of what plans Oda has for Pez, and I'm currently at a loss. There would have to be a rather significant timeskip for Pez to have any value to the story on his own, so for now he serves as a plot device/armor for Bege. Of all the monstrous things that we've heard Bege is capable of, his love for his wife and the pleasure he takes in being a dad have certainly humanized him beyond a lot of the things we can knock him for on the moral scale.