A 1838 biographical memoir of Joseph's son George includes the following:
'Joseph landed in Devonshire, penniless and unknown. The elegance of his manners, his extensive information, and the generous sympathy which the wrongs of his father-land had excited it the minds of Englishmen, secured him the friendship and the fostering kindness of the nobility and gentry of the county: amongst his warmest friends was Mr Patch, the eminent surgeon of Exeter who strongly recommend him to study that anatomy and surgery of the Teeth, a subject which had, at that period, excited little attention'.
In his will, Joseph refers to his 'Estate and Effects in Louisville Georgia North America'. This is where his bother Joseph Posner lived and ran a very successful boarding house and general merchandise store, although he later lost most of his money investing in a hot spring resort (perhaps influenced by this brother's experience of the hot springs of Bath?). Like his brother, Joseph Posner became highly respected. Very unusually he married a slave, Sylvia with whom he had son who died in childhood. When Joseph Posner died in 1820, he left money to his siblings: 'Dr Joseph Sigmond, now living in Bath: Dr David Posner, now living in the Kingdom of Poland, and his sister Diana'. We know from a notice that Joseph Sigmond placed in the Bath Chronicle, that David Posner died in 1823. We have not been able to find any information about Diana.
Joseph and Catherine's son George Gabriel Sigmond became a famous doctor and toxicologist. After studying at the Universities of Edinburgh and Cambridge and then at St George's Hospital London, he travelled widely in Europe before becoming the physician to the family of Sir Francis Burdett in Bath. He later became physician to the Marylebone Dispensary and Charing Cross Hospital in London where he lived. He wrote many professional papers, including 'Tea: Its Effects Medicinal and Moral'. There is no record of him marrying or of his death. But it is likely that he died in 1847, possibly abroad.