If you know Spanish, your can read it here https://lectortmo.com/library/manhwa/48898/kiss-me-liar it's a little less confusing
Do that person or omega is his mom, from what I gather they made him mad and he escaped and when they caugh him they let him choose a jewel, to appease him, Keith was the one that they asked to help him choose one, since he, Keith, is his, the white haired omega, son and all. They're family is weird and this omegaverse is not the same as the rest. It looks like only the omegas can mark a partner for life, which is new.

First of all, thanks to translator I get that angel gave birth to keith, and the person with grey hair was him. The thing is idk why he gets a jewelry when he escapes? Like what’s the reason and why he is escaping? Is jewelry a reward or punishment??? Me know only confusion(〜 ̄△ ̄)〜