Is a will, drafted with the "help" of a relative,who is the main beneficiary under it, likely to be valid, if and when probate is applied for, after the testator's death?


No – providing opposition is filed to the probate application, and the court (civil or religious) dealing with the case is persuaded that the beneficiary "took a part in the making the will", which is prohibited in Israeli law and likely to result in the will's cancellation.