Oh My! That does tend to put the proverbial cat amongst the pigeons doesn't it?
The info that I have (had??) is that Robert Liddle (the Yeoman) and his wife Ann (surname unknown) had three children - William, b 1823; Mary (b 1825, died 2 days old); and Elizabeth (b 1828). I have followed some of Elizabeth's descendents, and have also (a year or two ago) have been in contact with one of them.
The other Robert Liddle (the Brewer) and his wife Ann (Surname also unknown) appear to have had nine children - Sarah, b 1816; Ralph Robson, b 1819; Ann, b 1822 (died 8 weeks old), William, b 1823 (my ancestor, born in Newcastle); Margaret Robson, b 1824; Mary Ann, b 1826 (died aged 2 years); Dorothy, b 1829; Matthew, b 1832 (died aged 2 years); and Charles Thomas, b 1835 (died 9 months old). You also referred to a Robert (in earlier posts), which, if correct, makes it ten children.
There is definitely one, possibly two other Robert + Ann(e) pairings that I know of who were alive in the same time frame and areas as the families above.
I too found the 1816 marriage of Robert Liddle and Ann Robson, but according to the parish record (I have a photo of the page) he was a labourer and could not write, so I am very uncertain that that pair are the parents of any of the above kids. It is also the only Robert+Ann(e) marriage that I have found, despite much searching.
Your marriage certificate for Elizabeth raises the possibility the the two Williams listed above are one and the same person, although why a child born in Newcastle should be baptised in Morpeth (quite distance in 1823) is a question I have not been able to answer satisfactorily. Perhaps that is one you can answer!
Regards,
MoBear