The surname Luffman is rare(ish), there are around 2400 bearers worldwide, around 550 in the UK, a similar number in Canada, 1200 in the USA and the rest worldwide, but mainly Australia. (Under 100). Before John's own marriage at Alford in 1797 there is no record of the surname known to me in the North of England, the heartland of the surname being in Dorset, Hampshire, Somerset and Wiltshire. The bulk of those in Dorset, Somerset and Wiltshire are clustered in a small area around the northeast of Sherborne (Dorset) but though geographically close lived in three counties, which means my research covers these three record offices instead of being concentrated on one. John and his wife, Ann, had at least three legitimate children. At marriage she was recorded as a widow; having had 4 known children, one b 1785 with her husband Edward Troy, who then vanished, two others with unknown father(s) b 1790 and 1793, a further daughter b 1797 who as my ancestor was then on the scene I think was his daughter born before marriage, and three sons b1798, 1804 and 1805. The entire family descends from the eldest son, also John, and primarily from his 5 sons born between 1818 and 1828. He also had two daughters. The second son Thomas though married had no recorded children; the third son William married three days after committing a highway robbery in 1832 and was transported. He and his wife had no children that I could find. All John's three children were born in Alford Lincs.
During 1797 seven soldiers from the Somerset Militia married local girls while stationed in Alford, so my case is probably not unique.
As you see, it is quite complicated, I was trying to keep it as simple as possible to avoid confusion.