As posted by ev I feel sure that Cecilia O'Brien was Cecilia McGowan born 1932, mmn Crombie, who married an O'Brien (can't name him as possibly still alive) in 1956 Tradeston - you easily find his Christian name by looking at the marriage entry.
You refer to a sister 'Nora' - think this was a nickname/pet name as she appears to have been born as Honor McGowan 1938 - married to Osborne (can't name in case still living) in 1963 Tradeston. She died as Honor Osborne 73, mmn Crombie, in 2011 Glasgow Martha St. R.D.
Looks like a brother Philip McGowan was born 1923 Govan - he died in 1982 Renfrew (mmn Crombie).
Their parents - as stated by ev - appear to be Philip McGowan and Cecilia Crombie who married 1921 Govan.
There is a tree on Ancestry stating Philip McGowan (tree gives his middle name as Fowley - his mothers maiden name - but birth/marriage/death are as plain Philip) born 17/1/1897 to a John McGowan and Bridget Fowley who married 1893 Govan - the tree also includes photos of both John McGowan and wife Bridget. The tree states Philip McGowan died 1946 (no details of where) but this is untrue. He died 11/4/1943 Knightswood Hospital, Glasgow, home address 109 Neptune Street, Glasgow (you can actually view the death certificate on SP by buying some credits) and confirms his wife was Cecilia nee Crombie.
I would suggest that you concentrate on one person/family at a time, buying certificates as needed initially to confirm details as you are effectively starting off 'blind' with names but no details.
Annette
