MILLER seems such a straight forward name to research but do not overlook the variants. For Example - the marriage of John to Mary INKER is in our transcripts of St Saviour's Puxton
23 March 1773 - John MILLIER of Puxton to Mary INKER of Puxton by banns -witnessed by Mark MAY and William NEIGHBOURS. Both of the witnesses signed many other marriages at Puxton so they are unlikely to be related to either family.
There are christenings of children of John & Mary MILLIAR at Puxton, including a William in 1786. I noticed that one of these children was called Grace and that a Mary INKER was christened at Huntspill in 1750 d/o John & Grace - is that the Mary INKER who married John?
There is a George MILER aged 1 in Winscombe on the 1841 census and it looks as if his parents might be William & Sarah (no relationships on the 1841 census)
George is christened as George MILLIAR in Winscombe and the baptism gives his place of birth as Sandford. Do you have his birth certificate? - I see he was registered as George MILLIER.
If Sarah was his mother - and her age of 78 was correct when she died and was buried in Winscombe as Sarah MILLIER on the 10th June 1866 - that makes her about 52 when George was born.
I see when William MILLIAR married Sarah SMITH in Winscombe in 1814 he was said to be of Yatton - presumably he was living there at that time or at least in Puxton.
If Mary INKER was from Huntspill it is possible that the John MILLEAR christened in Cossington in 1750 might be her husband. I found these two who are outside of our area by using FreeREG - but perhaps you have already discounted them.
John Millier b 1750 Puxton, d 1793 Puxton married Mary Inker 25 March 1773. A son Joseph Millier b 16 Dec 1793 Puxton (presumably their last child) married Ann Exon d of Joseph Exon 16 Nov 1818. Mary Millier b 1820 Sandford married William Saunders 6 Dec 1840 in Bristol.