A three-year-old boy struggles to thread beads on a string while his older sister watches. She could ignore him or take over the task to get it done quickly. But if she observes him closely, and realizes that he is struggling to hold the string steady, she could offer to hold it for him and praise him for any beads he threads.
This approach — which includes awareness of the child’s cues, clear communication, back-and-forth reciprocity and guidance that adapts to where the child is at — would be an example of the sister “bridging minds” with her brother.