A younger son of
England's King
Edward III. You have run into him if you have read or seen
Shakespeare's
King Henry IV Part I or, perhaps, an
avatar of him if you have seen
My Own Private Idaho. He was the father of King
Henry IV by his first wife and later married his long time mistress, Katherine Swynford, who was sister-in-law to
Chaucer. His children by her were the
Beauforts, a family heavily involved in
The Wars of the Roses and very tied up in the lineage of the English Royal Family. He was one of the major wheeler-dealers of his time.
UPDATE An evening with my battered Bard reminds me that you have to have seen Richard II, not Henry IV Part I, to get your full of old John. He died before Henry IV finally offed Richard. But his spirit still hovers over Prince Hal and his Dad.