Question: Is there any way, according to Torah law, to determine during my lifetime who should inherit what I leave behind, and is it proper to do so?
Answer: Torah law is very specific about the rules of inheritance and the priorities it assigns differ in many ways from that of civil law. The only way one can determine his own priorities according to Torah law is to make a gift during his lifetime of what he wishes to bequeath to a particular recipient. The Talmudic Sages provided a formula for doing so while retaining the use of the bequeathed property. A will is written in which the ownership of the property is transferred to the beneficiary but use of it remains with the benefactor until his death, at which time it also reverts to the beneficiary. One should consult a rabbi or a religious lawyer familiar with halachic preparation of wills if this is what he intends to do.
In regard to the propriety of making any such arrangement, a few considerations must be borne in mind.
Disinheriting a son, even if he fails to live up to the spiritual standard expected of him, is frowned upon by our Sages because there is always the possibility that the offspring of that wayward son may be righteous Jews who will benefit from the inheritance.
Favoring one son over another in distributing the inheritance carries with it the seed of fraternal discord, as we learn from the hatred Yosef suffered from his brothers because of the favoritism to him shown by their father.
Finally, there is the issue of leaving money to charitable causes. While there is halachic restriction on a Jew giving away so much money that he risks impoverishment, this does not apply to what one gives to charity at the time of his death. There is a difference of opinion amongst the halachic authorities as to whether this means that he can give away everything or whether to leave half or two-thirds to his heirs.
If one is inclined to giving charity in order to gain great merit for the World to Come and wishes to avoid any problems, he should make such contributions during his lifetime, thus not only gaining credit for his afterlife but extending and enriching his life in this world.