I have just found the following on another tree but they have stopped at the death of John
John Higgins
born October 1881 Mullaghdroma, Cloughbrack Upper, Clonbur, Galway, Ireland
Died July 1996 Gaillimh, Galway, Ireland
Married Anne Burke 1913 Oughtererad
John's parents
Patrick Higgins
Catherine Klyne
Still no sign of two boys born to John and Anne. So I have no idea how they are not registered but at least one has gone on to have a family.
Thank you everyone for your help. It is appreciated