Hi Catie - & Kenjo
With Kenjo's 1871 census, I am still more convinced they are the your family. Ages can be notoriously out on Census - as these 81 & 71 show if these 2 census are the same family, and I really believe they are! Place of birth can also be wrong for various reasons, I've found countless proof of this in my own family research.
You've a list of children that do not include any before 1858, yet the parents married 1848. Given they seem to be quite prolific with the issue, I'd wonder about there being others prior to 1858 - ie: 22 yr William off the C71 and 27 yr old Henry from the C81. You also have a Glasgow connection to go with the family belief, ie: the birth of Henry, though in 1871 it says he was born Stirling.
By 1881, Mary from 1871 could be married, or working/living elsewhere and William is probably here in 1881:
Dwelling: Wests Land
Census Place: New Kilpatrick, Dumbarton, Scotland
Source: FHL Film 0203551 GRO Ref Volume 500 EnumDist 17 Page 27
Marr Age Sex Birthplace
William REYNOLDS M 31 M Milngavie, Stirling, Scotland
Rel: Head
Occ: Gardener (Dom Serv)
Elizabeth REYNOLDS M 28 F Lonmay, Aberdeen, Scotland
Rel: Wife
Jane REYNOLDS 8 F Maryhill, Lanark, Scotland
Rel: Daur
William REYNOLDS 3 M Milngavie, Stirling, Scotland
Rel: Son
ALso, it occurs to me that CONNOR and CONNELLY could be mistranscribed for each other - the brother in law in 1881, could be a CONNOR, or could Margaret have been a CONNELLY rather than a CONNOR?
Anyway,
I certainly wouldn't write off the 1881 / 1871 families. It is also Anthony in the 1881 that helps strengthen the links - it's not that common of a name, I don't think, for there to be a lot of them about of the same name with the same named parents and same named siblings (give or take one or two )as you are looking for?
Isn't genealogy fun? I often wonder at why or how things seem so muddled on Censii - I like to picture entire families sitting about after the Census man has gone, saying " Crumbs, I told him wee Mary was 8, I forgot she's 10 now". I can also imagine a father of many children forgetting which one was what age !!
Good luck Catie !
Cheers
Anne