My great great great grandfather was born Frederick James Percival in 1840 Lambeth England, he married and had several children born under the name Percival, he then migrated to USA to work on the Canadian Pacific Railway for a few years, two more children were born there. Then the family moved to Australia in 1882 , two more children were born but they were registered as Percival Carson, eventually the percival was dropped and they became Carson. When Frederick and his wife died they were burried under the name of Carson with no mention of Percival and future generations have only just discovered this.
I guess we will never know why he chose to do this, he certainly kept it a secret. He was only ever refered to in Australia as Mr Carson.