If you mean working together, then my answer is yes. Examples of that collaboration include joint supervision of dissertations, and joint research projects. In another situation where you mean coincidence, then my answer is it is a probable issue, but the probability that they follow the same approach is not highly probable.
Yes, indeed it is a common practice among different researchers. You might have noticed in different research papers that different institution names are appearing with author names. It mean researchers from different institutions worked together on one research.