The John Thomas s/o mathias Cowley appeared to be christened Lon 1840-02-23 and is age 11 in 1851c
whereas your John is christened Mar 1832-09-30 and is age 8 in 1841 (and presumeably 18 in 1851)

the former John Thomas would appear to better match the Cronk moar so I suspect the genes united lady may well be correct