Hi Sheldon,
In 1901 Census, at 8 Malloch’s Close Canongate Edinburgh
Hugh McMahon 32 b 1869 Edinburgh Midlothian – Brewery Labourer
Catherine McMahon 26 b 1875 Edinburgh Midlothian Wife
Hugh Patrick McMahon 10 month’s b 1900 Edinburgh Midlothian
As census was 31 March 1901 and he was 10 months old, he would be born in May 1900.
On ancestry, there are 5 Mary Halls born just before turn of century, not sure what one, but marriage certificate should give parent’s name
Tom