Brother, sister

(Jane is crying.)
Thomas: Jane's sad, Mama.
Me: Yeah, I know. I'm not sure what she's upset about.
(Actually, I knew why she was sad. She was sad because I took a toy away from her in order to change her out of her onesie that was covered with food. Jane does not like to be changed.)
Thomas: I know why she was sad. She was sad because she couldn't see me.
(He wasn't wrong. She stopped crying the moment she saw him.)