My information is that Alexander was a twin, but of Aulay, not Penelope. He was born in 1758 and died in 1800. He was minister in Cardross (where his father had also been), married Margaret Ewing, and had 4 children: John (b Sept 7, 1793)
Jean (b May 31, 1796)
Thomas (b Sept 13, 1798
Margaret (b July 5, 1800)