Yeah there have been at least two attempts.
According to the A-Z John Morrison argued the quarrel that J Kelly had with his wife was over an affair with MJK. Asking around on his escape he tracked MJK down killing those he asked (i.e. JTR's other victims). (1996:213)
James Tully on the other hand suggested that MJK was Mary Brider, Sarah Kelly's sister and hence James Kelly's sister in law (1998:325)