H. use Whose as the possessive form of who. (e.g. This is George, whose brother went to school with me. We saw some people whose car had broken down)
H1. use whose mostly for people. (e.g. I met someone whose brother I went to school with. (I went to school with his/ her brother) I met man who knows you. (he knows you) vs. I met a man whose sister knows you. (his sister knows you) We met some people whose car had broken down. Ken, whose car had broken down, was in very bad mood.)