In the 1841 Census William Lucas is shown as age 70 and as in that Census ages were generally rounded down to quinquennial ages, i.e. he could be any age from 70 to 74, that gives his year of birth as between 1766 and 1771. With at least 6 baptisms of a William Lucas taking place in the London area in that period it not easy to be absolutely certain which if any is the correct one.

However, I think the most likely baptism for William Lucas is the one at Wapping in 1770 and I have assumed this is the right one. William's son Francis by his first marriage married a Caroline Huddy. Her father, Christopher Osborne Huddy married (in 1791) Elizabeth Ann Lucas, then a minor, who would be William's sister. There is also a marriage in 1802 between Charles Huddy and Sarah Lucas; this could have been William's other sister but I haven't found a relationship between Charles and Christopher Huddy. Furthermore, William & Sarah Lucas were the witnesses at the marriage of Christopher Osborne Huddy to Elizabeth Ann Lucas.