Have read the other posts and done some research trying to stick only to facts rather than the info. (most of it wrong) posted on online trees.
First, with the exception of 1, none of the Butlers Marston baptisms are in online records - you need to have a check made of the records to confirm although my instinct here is that the parents - George and Susannah - are correct.
Children:
William bp.27/7/1806 Butlers Marston (submitted entry no parents shown) - he married an Elizabeth Smith 16/1/1827 St. Martin, Birmingham and lived in Butlers Marston 1841/1851.
Sarah bp.29/6/1808 Butlers Marston (submitted entry no parents shown) - she married Thomas Brown 21/1/1838 Leamington Priors (father shown as George). Living in L.P. in 1841 and Susannah Tustin living with them. In 1851 still there but husband shown as a William (?).
Ann bc.1811 (nothing submitted) bur.21/8/1829 Butlers Marston
Elizabeth bp.7/3/1813 Butlers Marston (submitted - if correct she died between 1813 - 1815)
Elizabeth bp.8/4/1815 Butlers Marston dau. of George and Susannah. This is an extracted entry. She married a Stephen Prophet 12/10/1837 Leamington Priors, shown as dau. of George.
Hannah bp.22/2/1818 Butlers Marston (submitted entry). She married James Clarke 20/5/1839 Leamington Priors (father shown as George).
Lucy bp.16/12/1821 Butlers Marston (submitted) - bur. 26/9/1822 (NBI) aged 9 months.
Lucy bp.17/8/1823 Butlers Marston (submitted - in 1851 she's single and working as a Cook in Leamington Priors).
George bp.15/10/1826 Butlers Marston - submitted, as you know and the subject of this topic.
We know that George bur.19/7/1831 Butlers Marston (NBI) was aged 44 so born circa 1787. According to 1841 Census Susannah Tustin, his widow, was bc.1781 - she appears to have died in 1843.
If the Birmingham marriage is correct it seems unlikely that George would have been a widower as only 19/20 when he married. Perhaps it was Susannah Marr who was a widow? since she seems to be 7/8 years at least older than him.
Anything further right now is just conjecture which is the situation you are currently in. You have to get a check made of Butlers Marston baptisms to confirm they are all to George and Susannah, and check the details of the Birmingham marriage which might not even be the correct one. Just because dates fit doesn't make it so.
One step at a time - ignore the conflicting and mostly wrong information that's online at the moment and check the facts.
Annette