Will a mother be sinful for addressing her son, who underwent a sex change operation to become a female? How will the inheritance be distributed after the father's death? Is avoiding a maternal uncle who underwent a sex change operation considered severing ties of kinship if this is based on doctors' advice to protect the children from psychological harm?

The issue is significant and requires presentation to scholars and doctors to determine the individual's true gender (male or female) before issuing a Sharia ruling.

If your brother underwent gender reassignment surgery from male to female despite being biologically male, he has committed a great abomination. His Sharia rulings are those of men in all matters, including inheritance.

He must be treated as a man, and it is not permissible for your mother or anyone else to treat him as a female.

The principle is the obligation of maintaining kinship ties. However, if seeing this brother harms the children, then there is no sin in severing ties with him until the harm is removed.