Does a firstborn son receive a double portion in inheritance?

Greetings,

In principle, yes: the firstborn receives a double portion, as stated explicitly in the Torah (Deuteronomy 21:17), and so it is in Shulchan Aruch, Choshen Mishpat (section 277, paragraph 1), that the firstborn receives a double portion in his father’s property.

That is, if, for example, there are five sons, the inheritance is divided into six parts, and the firstborn takes two of those parts (Sema, small commentary 2).

However, one must know that the firstborn receives a double portion only in the father’s property, but not in the mother’s property (Shulchan Aruch, section 278, paragraph 1). Therefore, if the father passed away before the mother, and the children gave his estate to their mother, then after her passing the firstborn does not receive a double portion.

There are also several other details, such as the fact that a firstborn who was born by cesarean section does not receive a double portion (ibid., section 277, paragraph 7), even in the father’s property.

Likewise, he does not receive a share in assets that are expected to come into existence only after his father’s death, but only in assets that were already in his father’s possession and came under his control, as it is stated: in all that is found with him (ibid., section 278, paragraph 3). There is also discussion as to whether money in a bank is considered expected assets or assets in possession (see Ashrei HaIsh, Choshen Mishpat, part 30, paragraph 9).

Therefore, you should go to a rabbinical court, where they will hear the exact case, clarify the facts, and instruct you how to proceed.

With blessing,

Hillel Meirs