there is a little complication though!!!!!
1851 mother is Mary Ann
1861 mother is margret
they seem to be same person going by age and p.o.b.
but
1861 son James age 14 lab at Iron works b Mon - is transcribed as James Prothero -and on image his name is dittoed as Prothero
however
in 1851 James is transcribed as James Prothero age 3 -but image reads James Prichard?

then FreeBMD there is a marriage regDec qtr 1847
Monmouth
26 99
on same page (among others)
John Prothero
Margaret Davies
Mary Anne Pritchard
so could this be your John's parent's marriage

and which one did he marry??
If it is mary Anne then did she have an illegit son James -or had she been married previously???
a puzzle
Suz