I'm coming to this a bit late, but hope it will help. I recognised a few names in your post from the will of a distant relative, Peter Hurst (1779-1849), leather dealer from Ormskirk. He married twice but had no children. His second wife was Ellen Taylor, for whom I have no parents names, but Peter was a Catholic so I am guessing Ellen was, too.
Peter left a lot of bequests to various nephews and nieces, which have helped to piece his wife's family together a bit. Specifically, he mentioned the following brothers-in-law and sisters-in-law -
Margaret Rigby (Margaret Taylor m. John Rigby 21/4/1798 St. James, Toxteth?), who had a son William.
William Taylor (deceased), who had children named Martha, William, James. [This James had a daughter named Jane and a deceased daughter, Mary Almond.]
Thomas Taylor (deceased), whose children were John Taylor and Elizabeth Riding. [I believe there were also two more girls, Mary and Alice.]
Mary Fazakerley (Mary Taylor m. Edward Fazakerley 28/12/1782 St. James, Liverpool?) - she had sons named Edward and John; John's children were named James Fazakerley, Thomas Fazakerley, Edward Fazakerley and Grace Stock.
There is also a mention of Mary and Alice, daughters of Thomas Fazakerley. I presume these are the great-grandchildren of Mary Taylor/Edward Fazakerley.
However, going by the fact that Peter's will was made in 1849 and the only marriage between a Grace Fazakerley and a Stock that I can find is the 1815 one to James Stock, I think the wording of the will had become confused. (John Fazakerley, son of Mary Taylor, did have a daughter named Grace but she was only about 7 years old in 1849.) I have never managed to find Grace and James Stock on the 1841 census, so your detail about the emigration would explain that.
Hope the above details are of some help. I do have a transcription of the will, which I'm happy to pass on