William Douglas (died 1791), a Scottish ship captain and maritime fur trader

[William Douglas]

William Douglas (died 1791) was a Scottish ship captain and maritime fur trader during the late 18th century. He worked with the British trader and Captain John Meares, commanding the ship Iphigenia Nubiana. He was involved in the Nootka Crisis of 1789, which brought Britain and Spain to the brink of war. A few years later he was captain of the American ship Grace. In 1791 he partnered with Captain John Kendrick in an attempt to open trade with Japan.

Iphigenia Bay, in Alaska, is named for Douglas's ship, as is Iphigenia Point in British Columbia. In Haida Gwaii (the Queen Charlotte Islands), Coneehaw Rock is named for a Haida chief with whom Douglas traded and exchanged names. Douglas Rock is located nearby.

Dixon Entrance, between British Columbia and Alaska, was given the name Douglass Entrance by Meares.

I am keen to find details of his family.  Can anyone help?