WHOLE CHARACTER
爷yé
grandfather (爷爷); a respectful term for an elder man; (old) a master or official (老爷); god (佛爷, 财神爷)
爷 is grandfather — and an old word of respect for any grand older man.
The header says the older 爺 was 形声 with 耶 as the sound side; the simplified form keeps the father radical over a reduced piece, so no sound rule is taught.
MEANING: FATHER (THE RADICAL 父)
父fù
father
Father-related clue in 爸.
In 爷: meaning: father (the radical 父) ZDIC lists 父 as the radical.
REDUCED LOWER-RIGHT PIECE
卩jié
a seal; the kneeling-figure form
A bound piece; in 爷 it is the reduced remnant after simplification.
In 爷: reduced lower-right piece A reduced piece left by simplification; it is not the old sound piece 耶.