The value of knowing the witnesses at a marriage is illustrated by this recent email:
Date: 18/02/2012 05:32 PM
Subject: James Adwick Waller
Just been visiting your excellent site by trolling the internet looking at the Hadwick family and as your site was very helpful to me I thought I should provide some info for you!
The important one was the identification of James Waller baseborn son of Ann Waller, baptised at Harting, Sussex, as James Adwick Waller.
... Importantly for you however is the movements of James Hadwick/Adwick/Addick as James Hadwick and Ann Waller were witnesses to the marriage of Anthony Knight, widower, of Sheet [near Petersfield] and Ann Carpenter, spinster, of Rogate, Sussex at Petersfield, 13 July 1833. This is 10 months before the baptism of James Waller at Harting on 13 May 1834, one wonders if there was a great deal of partying after the wedding!!! Also interesting is the fact that the baptism is shortly before the burial of Henry Adwick at Harting on 18 May 1834. Possibly James was attending his brothers funeral, though this could be a coincidence. When James Addick is married to Ann Cannens on 4 April 1852 in Petersfield his father is named as Henry Addick. From Census records etc this James was born 1811x17. Henry was 25 at his death in 1834 and therefore born 1808/09.
Though it's not definite it would appear that James Adwick Waller is the son of James Adwick. The latter is probably the son of Henry Adwick. ...
Obviously, a lot of this is guesswork at present but I hope it's of interest.