In California, over the years, I have handled many cases involving disputes between family members over the estates of a deceased relative. Brothers against sisters, sisters against brothers, uncles against nieces, nephews and others. Some cases go to trial; other cases settle. In all events, however, someone is going to be disappointed with the outcome, which disappointment can occur even if they prevail.
If you have been disinherited, you believe that the instrument that disinherited you was obtained by undue influence or when your deceased loved one (or relative) was incompetent, your recourse is the courts. Let’s say that you succeed in getting the offending instrument (a will or a trust) thrown out. What then?
The court may say that if there is no other earlier instrument, the estate will go by intestacy (as if the decedent died without a will) and it will then be divided among the heirs of the decedent. However, if there is an earlier instrument (perhaps a will) in which you have also been disinherited, then prevailing in the trust contest only sets you up for the next contest, which is to challenge the will (presumably on the same grounds as you challenged the trust).