Okay, this is where my current thinking is..
My Grandfather Edward Booth is Edward Gribben Booth / Teddy Gribben dob 03/02/1900
His mother is Rose Ann/Anne Gribben born c1871
Rose Ann Gribben is listed in 1911 census as Widow. Address is 48 Kent St, Belfast.
Dont know if she was born Gribben, married Booth (who died) then reverted back to Gribben, or if she never married at all, or if she was born Booth, married Gribben (who died before Edward was born) so she kept the Gribben name, although this doesnt explain why Edward changed from Gribben to Booth as he got older.
Do any of you know what common practice was back then for widows / unmarried mothers?