Thomas Mullarkey - Sylvia Coales

This may be a long shot but if any one has any information on Thomas Alfred Benedict MullarkeyBorn sept 22nd 1910in Elham Folkstone UK who married Sylvia Phylllis Coales born April 17th 1911 in London?. They married 27th october 1931 and have 4 children born within this marriage Patricia, Raymond and Colin, The oldest child Frederick Mullarkey is my Grandfather born 1927 who has now passed away. What i am trying to discover is who my granfathers real father is as he was adopted by tom Mullarkey. I've been told that my great nan worked for a family in london as a nanny when she fell pregnant with my grandad at the age of 16 and was not married etc.