No source was supplied for Alexander Nisbet being the father of Moses Nesbitt. In my research I have not uncovered documentation for any parent of Moses Nesbitt.
I doubt this Alexander Nisbet was the father of Moses Nesbitt. The Geni profile of Alexander Nisbet claims Alexander was born in 1671. Moses was born about 1740. Alexander would have been 69 or 70 at the time Moses was born. This age is highly unlikely for a man to father a child in this era.
In addition, the Y-DNA of male descendants of Moses Nesbitt indicates his male line is of Irish descent going back to the 9th century. Alexander Nisbet was born in Scotland in the 17th century.