Hi Namma, there is a tree which has Alexander as 27 at time of marriage Elspbet bn Leochel Aberdeen 1805, 26 at time of marriage, father John 1781 to 1853. I hope this helps you to find her baptism etc.
Tinam
p.s 1851 census Alexander 47 stone dyker, Elspet 46, Alexander 18, John 16, Mary 12, Joseph 9.
Civil Parish of Coull.