What were the names of his children?
Scottish naming patterns were very often adhered to.
The first son was usually named after the paternal grandfather; the first daughter after the maternal grandmother etc.
Have you seen the entry of William's marriage to Mary Peterson in 1842 at Bervie?
Does it give any further information?
I see familysearch has that marriage, (film no 993310), and also a repeat one at Arbuthnott (film 993387).
You can view the OPRs of both places on familysearch at one of the LDS libraries. They may (or may not!) give some extra information.
familysearch also has a John Strachan bap 28th March 1825 at Laurencekirk. Father Alexander, mother Ann Jack.
This is the only Strachan baptism at Laurencekirk that comes up between 1810 and 1825.
familysearch also has several Strachen children baptised at Arbuthnott - just down the road, in the timeframe you're looking at. Mostly with father James. Unfortunately no William.
Possibilities: His age is incorrect on the Censuses; He wasn't baptised at Laurencekirk. but somewhere else: He was not baptised at all.
Good luck!
