Hi,
I am also in Australia an am a descendant of William Edward Scott who was a master mariner. I do know a lot about him, but the problem is that he may be one of two people, and you might be able to solve the mystery.
If I look at the names of William's children, then there is a very strong resemblance with the names of children of your ancestor, James Scott. The names Eliza Sophia, Amelia Ann, Elizabeth Mary and William appear in both family trees.
However, if we subtract his age from the date of his death, then my ancestor was born on 28 Jan 1765, but there is no proof, only one wrong assumption. If you have proof that the brother of your ancestor was born in 1767, then I know that I am on the wrong road. Have you come across records that indicate that William was indeed born in 1767? Was this just an assumption? His parents, William and Elizabeth Matthews were married on 16 Sept 1763, and it is therefore possible that their first child could have been born in 1765 or 1767 according to your information. I need to translate all my research from Afrikaans and will do so once I know that we are indeed talking about the same William Scott.
Having read all the correspondence, I may just mention that here is a good reason why William did not inherit anything. William was captain of a number of ships and was an expert master mariner who sometimes had to pass new ships as being seaworthy. He sailed between South Africa, Mauritius and England between 1797and 1821 and died in Cape Town in 1847.
Kind regards
Johan