Henry VIII has accomplished it - what with the current duchess of Cambridge descending from his affair with Mary Boleyn. While Charles II got it right with Diana Spencer (amongst others) marrying Prince Charles.
Richard I left one bastard, Philip of Cognac, who married a French heiress (who died without issue). WI Philip had remarried and left at least one child who later married into the English aristocracy, and somehow, Richard's bloodline (tainted though it may be) returns to the main line of the later kings of England.