I would guess that there are probably between 3 and 5 John Lowes.
1) the one who married at Stamford in 1780
2) the one who was fathering children in Billinghay in the early 1800s (wife Mary) - this one seems to have a brother also fathering in Billinghay around the same time (Thomas).
3) one who married in Stamford in 1815
4) one who married in Liddington in 1818
5) one fathering children in Billinghay in the 1820s (wife Elizabeth).
3) and 4) could perhaps be the same one.
2) and 5) could be the same, or 5) could be a son of 2).
As there were baptisms in Billinghay in 1818, 1822 and 1827 and Stamford in 1816, 1819, 1820 and 1822 (not to mention in Belmesthorpe a mile north of Stamford in 1824, 1826, 1829, 1831 and 1832), I think it's asking an awful lot of John Lowe who was first married nearly 50 years earlier to be the father of all these children in places over 30 miles apart. The bicycle had not been invented at the time.
John Lowe (45, miller) and Elizabeth (45) were still in Billinghay in 1841 with Charles, James, Edward, Joseph, Ann and John.