Lisa, My tree incorporates large parts of the Burin Peninsula and I have records that may link up to the three brothers you are looking for.

Thomas had no sons. He had 1 daughter. I have no record of her marrying or having children.
Samuel had two sons. I believe both died before having children of their own.
William had six sons and three daughters. His descendants still live in the area.

You can use this link as a starting point: https://www.familysearch.org/tree/person/details/L6KC-M15