After grooming and tacking up, Kai and I did the pre ride checks and I rode him a little, working on bending so my sister could ride. Kai was doing wonderful lateral flexion and he was doing everything I asked him to do. I dismounted and helped my sister get on. I led her around the arena and reminded her to keep her legs relaxed and to not lean forward. I suggested that she sings a song so that she doesn't hold her breath. We kept on walking around while my sister sang and held her arms out to learn balance. Kai didn't look too impressed but he was behaving himself very well.
Later I took her for a little trot reminding her to sing so she stays relaxed. We also did some changes of direction at the walk without holding on. We were finishing up by waking on the rail and Kai nipped me, to my surprise. I flicked my finger on his muzzle but didn't correct him more because my sister was riding and I didn't want him to jump or become unsteady.
When she was done riding Kai yawned and yawned. I think he feels that she is unsure and it makes him feel a little unsettled.