Who is Vigor Miller from Seventh Son and what is their importance?

Vigor is Alvin Miller's oldest son. He is described as a strong, smart, brave young man who dies early in the book. Vigor dies while attempting to get the families' wagon, and his mother Faith across a raging river. He stays alive long enough for his youngest brother to be born, making the new brother the seventh son of a seventh son. Vigor obviously loved both of his parents very much to sacrifice himself for his mother.