Thanks Maddy52 and Jool - I will also bookmark this resource - very useful!
So William (1734-1779) and Mary, had 8 children, with the eldest Thomas (b. 1754), who married Sarah Heath. My direct descend was the 8th child James (1768-1853) - convict - sentenced to transportation for stealing a hat. (First Kiss in Australia).
Thomas and Sarah had a son, William Daniel Kiss - born Kenilworth 1776 - the solicitor.
So in regard to the 1791 'William Kifs, chaser and buckle maker, about 5 feet 8 inches high, about 28 years old, slender made, brown hair tied, fresh complexion, two or three scars on his forehead; supposed to be in London'...this could be William (1763-1836). He married Mary Hadnot in 1789, Shoreditch, London.
Could he have been on the run for 2yrs? Living with 2 families for a while? Need to find 1st marriage cert to prove this.
Thoughts?