Holden is the grandson of Dexter Alvin Dizznee, one of the members of the legendary Keeper Team. His parents, one being Dex's daughter, are also very powerful, with strong abilities. However, Holden's manifest came as a surprise to the family. Everyone was expecting him to be very powerful, but he ended up being a mere Vanisher. This led to isolation and eventually, to him being an introvert.
After manifesting, Holden attempted to keep his secret. He restricted himself with all his might, expecting another ability, but no. This was it. All he was ever going to be in life was a Vanisher. And with Foxfire and his friends pressuring him to manifest, he finally gave way, and revealed his ability.
The news came as a shock to the school. Both his parents had very strong abilities. And now him. His brother and sisters, who were older, and had already manifested, had much more powerful abilities, some even being as powerful as the great Sophie Foster herself. So when he revealed his ability, his siblings became awkward to be around him.
It had started with his siblings. Then it spread to his parents. Later on, most of the Keeper Team members simply shrugged their shoulders and moved on, training the other Keeper descendants, hoping they would "show results." But in the sea of skeptics, there were some believers too. Dex, his grandfather, had also thought some of the same things when he was young - that his ability was weak and not useful. However, Holden was done with his family members trying to make him feel good. It was always done awkwardly, and how was Dex any different?
Hence, he started going to Keefe, him being an empath. Keefe helped Holden get through his bad days and be there with him through his good ones, with his empathy ability. And of course, he taught him the ways of pranking - not that Holden ever used them anyways.
Keefe ended becoming almost like a parent to Holden, thus strengthening their relationship.