I have always been slightly confused about this William.

I have the following:
William DOUGLAS (Blacksmith) was born in 1819 in Jedburgh, Roxburgh, Scotland. He died on 20 Jan 1901 in Motueka, Nelson, New Zealand. He was buried on 22 Jan 1901 in Motueka Cemetery, Motueka, Nelson, New Zealand. He married Mary Ann HURREN on 25 Jun 1880 in Nelson, Nelson, New Zealand.

Mary Ann HURREN, daughter of John HURREN and Elizabeth SEAMAN, was born on 13 Feb 1823 in Kelsale, Suffolk, England. She was christened on 21 Mar 1824 in Kelsale, Suffolk, England. She died on 05 Oct 1916 in Kopuaranga, Wellington, New Zealand. She was buried on 09 Oct 1916 in Lutheran Cemetery, Mauriceville West, Wellington, New Zealand. She married William DOUGLAS (Blacksmith) on 25 Jun 1880 in Nelson, Nelson, New Zealand.

Other marriages:
COOPER, George (Ship Captain)
FRANKLIN, Robert Benjamin

Mary DIXON was born in 1819 in of, Jedburgh, Roxbrugh, Scotland. Mary married William DOUGLAS (Blacksmith) in 1841 in North Shields, Northumberland, England.

They had the following children.

Mr DOUGLAS was born in 1847 in of, Motueka, Nelson, New Zealand.
Mr DOUGLAS was born in 1849 in of, Motueka, Nelson, New Zealand.
Mr DOUGLAS was born in 1851 in of, Motueka, Nelson, New Zealand.
Miss DOUGLAS was born in 1853 in of, Motueka, Nelson, New Zealand.
Mr DOUGLAS was born in 1855 in of, Motueka, Nelson, New Zealand.
Miss DOUGLAS was born in 1857 in of, Motueka, Nelson, New Zealand.
Mr DOUGLAS was born in 1859 in of, Motueka, Nelson, New Zealand.
Miss DOUGLAS was born in 1861 in of, Motueka, Nelson, New Zealand.

Did he really marry a second time in 1880? And what took him to North Shields.

He apparently had a step daughter, Ellen.

Sorry - nothing on his parents - yet.