Archibald Erskine, 7th Earl of Kellie - Did Archibald Erskine had a child?

Edit:
I am trying to find out the parents of "Archibald Erskine Robson", originally from Anstruther. He could be Lord Archibald Erskine' son. My hypothesis is that A.E.R was a natural son, that didn't inherit the Lord title, and probably his mother was Robson.

A.E.R. came to Chile near 1820's , was captain of his ship, and he did some business with the new independent country, He later helped to start the nitrate business in Chile.