In the parish of St. Blazey, Cornwall in the 1820's, there were two William Stephens married to different wives named Elizabeth. This document seeks to determine which of them were being referenced in baptism and burial records.
 It appears that the older William and Elizabeth (nee Nicholls) lived at Highway, while the younger William and Elizabeth (nee Drew) lived at Restinnis. I am NOT certain that I have these correctly separated, but the following will detail my reasons for how I have separated them -- in the absence of any other information than the parish registers.
The Older William Stephens (b c 1773 m 19 Feb 1798 Elizabeth Nicholls)
From other trees on Ancestry.com, it appears that the older William Stephens was born at Gerrans, Cornwall about 1773. He married 19 Feb 1798 at St. Blazey with Elizabeth Nicholls (bap 12 May 1768 at Gerrans), when he was about 24 and she was 29, almost 30. (Her age leads me to suspect that she may have been a widow, with a different maiden name than Nicholls.) Since the younger William and Elizabeth did not marry until 22 Jul 1822, we can assume that the baptisms of children to William and Elizabeth Stephens prior to 1823 were all children of the older William and Elizabeth. They were all born at Highway in St. Blazey Parish:
 (Note that I only have the parish registers from 1813, so that any children born prior to that are not included here.)
The Younger William Stephens (b c 1788 m 22 Jul 1822 Elizabeth Drew)
There were three baptisms of children to William and Elizabeth Stephens after the younger couple married at St. Blazey. One of those was born at Highway, so that I have considered him as the son of the older couple, despite them already having a son name William for who I have found no burial record at St. Blazey. The other two children were both born at Restinnis. One of them was born in 1823, which further makes me consider the 1823 William to be the son of the older couple.
So here are the three children of William and Elizabeth Stephens baptized after 1822.
This is the best configuration that seems to fit the facts that I have available from the parish registers.