Fun part about Philip/Belos is you can take any behavior that Eda, Lilith, Dell (I lean toward him being Caleb's descendant due to the carving thing since Gwen doesn't seem to do it herself), and Hunter display and apply it to him.
The whole "BYEEEEE" thing since Hunter does it pointing to the possibility that it's not a Clawthorne thing. WHERE WOULD HE HAVE PICKED THAT UP, BELOS?! HUH?! HE'S NOT ALLOWED TO BE AROUND OTHERS, BELOS! WHAT DO YOU HAVE TO SAY ABOUT THIS, BELOS?!
Lilith's mannerisms. Hell, he could have seen a lot of what Lilith did during her time at the castle and had to try as hard as possible to ignore that she could have been just like him, if he knew, that is.
Eda's teasing and ego. Him toward his brother, at least.
They could have very well inherited it from him and not just Caleb. Caleb and Philip were brothers, after all, and orphans too so whatever Caleb did, Philip would have picked up on it and vice versa.