Meaning: This sentence tells us that a group of people related to each other expressed their gratitude to a dog for showing courage and rescuing someone from danger.
Choice of Words: The word "family" refers to a group of people related to each other, usually living together. "Thanked" means to express gratitude to someone. "Brave" means showing courage in the face of danger or difficulty. "Dog" is a four-legged pet animal commonly kept by people.