Strangely, I couldn't find their marriage even though it was registered in Liverpool (which you already have) - but I thought the church record would be there.

Name, Marriage, Date, Parish, Spouse, Parent Names:
Margaritam Cain, 12 Apr 1921, St Alphonsus (Alphonsi), Joannem Donlevey, Bernard Cain & Brigittae Cain.
Francescam Cain, 13 Nov 1915, St Alphonsus (Alphonsi), Patricium Aughes [Hughes?], Bernardi Cain.
Joannem Cain, 5 Nov 1919, St Alphonsus (Alphonsi), Mariam Moram, Bernardi Cain.
Francescam Hughes Aim Cain, 2 Oct 1920, St Alphonsus (Alphonsi), Gulielmum P Gorman, Bernardi Cain. [So Frances married twice?]

Sue