ソン, ゾン, まさ
suppose, be aware of, believe, feel
JLPT3 G6 S6 F577
The relevant seal inscription form combines an abbreviated form# of 在 exist + 子 child → *existence* represented by children/descendants (compare 孫)→ *keep*/settle (in place) (← maintain existence) → *know* (← have knowledge of what exists).
[Full Kanji Etymology List]