They had a daughter Joan de Beaufort. Henry never married and mentioned Joan and her husband Sir Edward Stradling in his will according to Albert E. Myers who mentions this fact in his Web genealogy. Verification of the lineage may possibly be found in an English database called Directory of Royal Genealogical Data compiled by Brian Thompsett. Be sure to check his Bibliography. The links I've provided in the lineage below certainly are only links, not proof.
Royal genealogies seem to bring the lion out in folk so tread softly.
Notwithstanding, I must add, it's fun stuff. BTW, Ralph Troop, a Sims descendant, has graciously offered to put the genealogy to the test on the RootsWeb Medieval list. We'll see what happens. I've provided links which will search their database and give you the results. When a tree gets to be that vast, you gotta wonder if there's truth behind the text.