Phillip

A person that’s repeatedly invited (and always shows up) to intimate family events/occasions, even though they are not family.
A Phillip is an outsider, but will be thrust upon the other members of the group as if they are legit and have always belonged. Anyone questioning the presence of Phillip will be met with contempt.
A Phillip will usually take more from an occasion than he/she adds.

“Why was he invited? He’s not even family! But he’s always turning up for shit that doesn’t involve him. He’s such a Phillip!”