I found this entry in 1901 and wondered whether it could be Margaret and Thomas, although Margaret and Thomas seem to have shaved some years off their age!:
Thomas Evans 61, Shipyard Labourer b. Ireland
Margaret Evans 41 b. Inverary, Argleshire
Thomas Evans 22, Ship Yard Labourer b. Irealnd
Robert Evans 13, b. Partick
Margaret Evans 8 b. Partick
George Seivewright 21 boarder
John McHoy 20 boarder
Address: 52 Crawford St, Partick, Govan
There is also a death on SP for a Margaret McGugan Evans in 1943 (b. 1859 from her death age) in Partick. This might let you re-confirm her parents' details if there remains any doubts. Just concerned about the birth place we are seeing for Margaret above, would be good to get further confirmation but struggling to see them in 1891 at present.
Monica