Bernard Mullen & Anne Cavanagh

Help!  I'm searching for my Nanny's parents, names unknown as she was adopted out to a family in Newry.  Through DNA I have found 3 links to the children of Bernard Mullen and Anne Cavangh but unfortunately there were 10 children!  The ones I can't find any further information on are:

Mary Anne Mullen B 2nd Jan 1892

John Francis Mullen B 15th Sept 1892

Maggie Mullen 23rd March 1894 

Patrick Mullen 23 June 1896

Rose Anne Mullen 1898

Catherine Mullen 1899

Eugene Mullen 1902

I'm trying to find a marriage certificate for any of them that will then hopefully lead me to a birth certificate for my Nanny.  She was born Mary Eileen 23rd March 1919 (We assume this is right).  The families births were all registered in Cootehill but address on birth records show Drumlood Co. Monaghan and the father was a farmer.

Any help would be greatly appreciated.  I'm at the end of all leads!!!

Thank you

Karen