If there is no will then of course there will be relatives who will have a claim to the estate of the deceased person. However, if there is a will, then those who are included are named and if someone is not named they should not be included and fighting for that is just greedy.
If Mickey Rooney didn't put them in his will then they should not be included in the estate. We have no way of knowing what they may have done and the reasons for not including them in the first place. Sometimes wills can come as a shock to family members who were expecting something, however their disappointment should not be more important then the deceased wishes.
If Rooney wanted those family members to inherit a dime he would have included them in his will. It was his money and property and should be distributed as he saw fit. The man left his wishes in writing and they should be honored. Going against what he wanted feels like stealing from the dead.
If someone makes a will that excluded certain family members, there must be a reason for the exclusion. If you disregard the will and include those people in the estate, then you're really setting aside the clearly stated wishes of the deceased, and that can't be right. I'm sure the excluded family members are upset, but Mickey Rooney made his wishes clear, and they'll just have to accept that.