Liz
Thanks again for your tips.
Have found Dennis's birth certificate and his mother Margarets death certificate.
Still no sign of Martins death certificate, Margaret died first in 1869 and I know Martin was deceased by 1881, I have tried all spellings. There is no record of him in the 1871 census, so he may have died soon after Margaret, though perhaps not in Scotland and thats why I cannot find him on Scotlands people.
If Martin died soon after Margaret the family would have been very young and perhaps Dennis was raised by Martins brother Patrick, hence the different fathers names on his birth, marriage and death certificates.
You gave me the info that Dennis had a brother Partick aged 1 in 1861, I have found a Patrick aged 10 living in boardings with other children in Ardrossan on the 1871 census, there is also a Martin McGurn aged 4. I still have to find out if they are brothers and if they are Dennis's brothers. They may have been fostered if their parents died soon after each other and none of the other family members were able to take them in. Thats my next task.
It would have been easier if they had given their children unique christian names, but then that would have made it too easy for us.
Cheers
Maggie