I believe that I've found Francis Cheynell's place in the tree. He was noted as the "first science fiction author," writing "Aulicus his Dream, of the King's Sudden Coming to London" in 1644, apparently, according to Wikipedia, an "alternative world" story involving the return of an exiled King Charles II to London. (Note: Charles II, Prince of Wales, went into exile in Spring 1646, and only returned to London on May 29, 1660, the restored king's 30th birthday. Someone with the time should better investigate this.)
If someone had found him earlier and has his profile elsewhere, please feel free to merge him.