According to an extensive list from a Mr. Marvin Ashby at firstname.lastname@example.org [the last email address I have for him], William Dews (son of John Dews) married Caroline Lister on 10 November 1844.You would have to discuss the discrepancy with Mr. Ashby.
Looking back on the list, which when I received a copy covered Dews in limited parts of Yorkshire from 1558 to 1900, I find the following entries:
Baptism 1 April 1821 William, son of John & Mary Dews of Horbury, Clothier - Horbury [source. Parish Records D3]
Baptism 19 September 1819, William, son of John & Elizabeth Dewes, - Marton with Grafton [no source listed]
Baptism 10 August 1794, William, son of John & Hannah Dews, Ossett - Dewsbury, All Saints [source: Parish Records]
Another William son of John in 1792, another in 1785.
Going in the other direction there was a William son of John baptized in 1831 which obviously is too close to the marriage date.
If you would like me to check for other children/siblings, please email me directly.Alternatively, contacting Mr. Ashby may be your best move.
I must stress that this list (as I have it) reflects those particular areas of Yorkshire where Mr. Ashby's interests lie.Therefore, the list is incomplete with respect to 'DEWS' in Yorkshire.