Do you have to cover your arms and legs in front of Mahram family? Can you specifically explain the rules of what is allowed to remain uncovered for men and women when they are with their Mahram family members?
It depends on the age and situation of you and the Mahram member of your family. It is not obligatory to cover your arms and legs in from of an old Mahram being sure that uncovering arms and legs will never cause nor initiate unwanted feeling. In general, it is not obligatory to cover in front of Mahram, that parts of your body which are usually uncovered at home with your family, provided that it should not cause bad feeling of desire or shame.
Wassalam.