It is permissible for the relative to ask for the inheritance even if that is done through the courts
You have the right to ask for your mother's right of inheritance, even if it means going to court, unless your mother allowed that. If your mother gave up her right to her brother, then you do not have the right to do that. The right is hers. But if she did not give it up, but she refrained from asking and disputing, then you have the right to ask and dispute for your rights, and there is nothing wrong with that. Praise be to Allaah. End quote.