Etymology of the word "grephew"

Original process

Niece (Greta, Naomi, Maggie) --> Greasy Niece --> The Grease

...as in:

"Hey there, Grease!"

"How're my Greases?"

"I need a Grease fix."

Parallel process (so the boys won't feel left out)

Nephew (Edwin, Javid) --> (do we really need to pretend there were any steps in between?) --> "The Grephew"

"Grephew!!!!"

"C'mere and give your (uncle/aunt/biological, adopted or honorary family member) some lovin', Grephmeister!