cheeks, jaw
頰 centers on the fleshy side of the face: the cheeks and the jaw area.
頰 combines 夾 (which likely contributes the sound) with 頁 (head), indicating a part of the head. The exact historical development is uncertain, but the phono-semantic structure is clear.
The left side 夾 looks like a person with something pressed between their arms, and the right side 頁 means head or page. Imagine pressing your cheeks between your hands while thinking about the head: 頰 is the cheek and jaw area.
For キョウ, imagine a person with very round cheeks trying to say 'kyou' (today) but it comes out puffy: kyou -> キョウ, and the puffy cheeks remind you of 頰.