Who is Alexander from Mayflower and what is their importance?

Alexander was Massasoit's son and Philip's brother. He was the sachem for the Pokanokets after his father. After being taken at gunpoint by the English over an "illegal" land sale, Alexander fell sick and died. It was rumored the English had poisoned him or contributed to his death in other ways. The English involvement angered Philip and Philip's actions toward the English were, at least in part, due to Alexander's death.