I should have said earlier that the sisters Mary and Ellen came from christening records in Haslingden, Lancashire when I was going on the assumption that Betty's father was Lawrence Duckworth, mother was Mary, all of Haslingden. This made sense to me since her daughter Betty Thwaites Ward died at a family home in Haslingden, occupied by that time by her daughter Alice Thwaites Thompson (1891). If all of you good folks are correct, I've been in the wrong neighborhood. Betty Duckworth Thwaites always appeared in the census as being born in Blackburn, so that could mean either Great Harwood or Haslinden, right?
I am prepared to let Mary and Ellen Duckworth go; they're both from Haslingden and their father was Lawrence.
Thwaites Brewery histories state Betty Duckworth was the sole heir and proprieter of her father's brewery venture with Messrs. Clayton and Dutton, so that's a problem with Grace being the eldest and also living possibly until 1855, and apparently never married. So is it possible Grace is not a daughter of Edward and Betty, but rather another relative buried in their grave site? Or perhaps Betty was chosen as heir over sister Grace for reasons other than who was the elder? Maybe Grace wasn't into beer??

The purchasers of the Roebuck Inn in 1897 (Thomas Duckworth in Rishton) were T. and W. Thwaites, of Blackburn. These would probably be nephews of Daniel Thwaites (son of Betty Duckworth and Daniel Thwaites), the millionnaire owner of Thwaites Brewery and Eanam Brewery. His heir was his only child and husband named Yerburgh.
I'll have to scrap my baptism of Betty Duckworth (Jan 1785, Haslingden) as it's based on a father called Lawrence.
Many thanks! I'll keep on plugging away.
Sally