There is only one birth record on IGI for a Thomas ELLISON born/christened in Blackburn between 1775 and 1795, that is:

Thomas ELLISON c.23 OCT 1789 Blackburn, Lancashire

Parents: John and Nancy ELLISON

John and Nancy also had: Ellen 1786, Catherine 1787, John 1791, Alice 1793 and William 1797.

Nancy may have been Nancy IRELAND married a Thomas ELLISON in 1777 in Blackburn, or even Nancy DOBSON married a Thomas ELLISON in 1773 in Blackburn, although neither appears to be a good fit with the children unless there were several unrecorded younger children.

If Thomas' mother was Nancy then that would explain his daughter's naming, however where the name Richard came from is unexplained.

Although Richard (1817) and Nancy (1819) are the only known children of Thomas, it is possible that Betty died after the birth of Nancy and he remarried. In 1821 a Thomas and Margaret ELLISON christened a daughter, Elizabeth, in Mellor. In 1823 they christened Sarah, again in Mellor. No earlier or later children of this couple are known. If the family moved to Mellor then a link is formed between Nancy ELLISON and her future husband, James FORREST, who was from Mellor himself. No marriage record for Thomas and Margaret nor any death/burial record for Nancy have been found so this all remains pure speculation.

The best fit 1841 census record for Thomas has a Thomas ELLISON 50 living with Ann 30, Catherine 4 and the SHAW family: William 30, Sarah 30, Martha 7 and Nancy 4. Perhaps Ann and Sarah were his daughters. The names Catherine and Nancy appear again. (HO107/502/16/24)