>His grandaughter
Here is another vid from earlier of the year with her. It it he refers to her as his grand daughter. Her body language looks like she is either shy to be on stage with him or just uncomfortable with him in general
https://youtu.be/vh_Ei0TeLe4
https://www.washingtonexaminer.com/news/biden-describes-granddaughter-at-12-as-a-little-butterfly-who-woke-up-with-a-snake-in-the-bed