The earls of Kent of this creation used Baron Holand (1353) as a subsidiary title; it became abeyant 1408. The first earl of Kent by this creation was the husband of Joan of Kent of the fifth creation.
The line of the earls of March became extinct with the death of Edmund, the fourth earl.
The Greys were a baronial family with substantial property in Bedfordshire and Buckinghamshire, and later around Ruthin in Wales. They rose to greater prominence during the Wars of the Roses. Edmund Grey, Lord Grey of Ruthin, started out a Lancastrian, but switched to the Yorkist side at the Battle of Northampton. He was a member of Edward IV's council, became Lord Treasurer in 1463/4, was created Earl of Kent in 1465 and was keeper of the Tower of London in 1470. He remained loyal through Richard III's accession, taking part in his coronation (1483).
Edmund's son George, the 2nd Earl, had continued as a Yorkist, marrying Anne Woodville, a sister of Edward IV's queen Elizabeth Woodville. (He was half-first cousin - both being grandsons of Reynold 3rd Lord Grey of Ruthin - to Queen Elizabeth's first husband, Sir John Grey of Groby.) He later married Catherine Herbert, daughter of William Herbert, 1st Earl of Pembroke.
The third earl, Richard, was the son of the second earl and Anne Woodville. He wound up heavily in debt, probably through gambling, and was forced to alienate most of his property. A good part ended up in the crown's hands; historians disagree regarding what this says about Henry VII's relationship with the aristocracy.
He was succeeded as earl by his half-brother Henry, son of the second earl and Catherine Herbert. Henry tried, with little success, to reacquire the property Richard had sold, and had to live as a modest gentleman, never formally taking title as earl.