Which of these would be the strongest transition from paragraph 1 to paragraph 2?

"But family is so much more than that" suggests that more interpretations will be coming in the following paragraphs. "Family has a lot of definitions" summarizes the first paragraph more than transitions to the next. "Some people claim they don't have any family at all" may move off topic depending on what comes next, and that is certainly not what is discussed in paragraph 2.