Taking care of one's aged mother

1. Please advise on the following matter.

A person was looked after by their grandmother from birth to until their grandmother died.At the age of 13 the person learnt that their mother did not want them at birth.The mother in the meantime married a Tamil man who after some time became muslim.The mother had another child and chose to look after the second child and felt uncomfortable around the first child.As time went on still staying with the second child who married a Christian lady and chose to be Christian the mother still stayed with child number 2. Many years after child number 1 married and migrate overseas due to being unemployed. Child number 1 benefited because the mother was working and had her house.As time went by child number 2 managed to transfer the house onto their name and now when the mother is old does not want to look after her.The mother on the other hand refuses to stay anywhere else as she has devoted her whole life to child number

2. What is the obligation of child number 1 as they reside overseas. Inshallah please advise on this important matter.