Charles and Mary LUCAS b.Ireland living in Saltney St, Liverpool in 1881 and 1891

The 1881 census for Saltney St., Liverpool shows my paternal grandfather, Christopher REID (mispelled as REED) aged 9 and living with his uncle and aunt - Charles and Mary LUCAS both born Ireland. There is no sign of young Christopher's father James REID (seaman b.c.1848) or mother Elizabeth REID nee SMITH (b.c.1852).

I'm trying to find where Charles & Mary LUCAS originated from also, where James & Elizabeth REID came from before Liverpool.

I found a marriage record for a Charles LUCAS & Mary FLYNN in 1870 Liverpool but am not sure if this is my LUCAS ancestors or not.

Can anybody help please.