to give, prepared for included in, embraced in
侅 centers on the act of giving or being included within something, with a sense of being prepared or embraced. The meanings are somewhat disjointed, but they share a theme of transfer or containment.
侅 is a rare character combining 亻 (person) with 亥, which may have contributed a phonetic element. The exact historical development is uncertain.
A person (亻) beside 亥, which looks like a container or a prepared offering. Imagine someone giving a gift or being embraced within a group.
For カイ, picture a person giving a kite (カイト) as a gift: kite -> カイ, and the person is handing it over.