Bava Basra, chapter 8, mishnah 4. This mishnah seeks to describe two differences that exist between a child's inheritance from his father and his inheritance from his mother. Therefore, the mishnah opens: "Echad" - there is no difference between a son and his brother, or a daughter and her sisters, inheriting from either of the two parents; "ela" - except for the following exceptions, where there is a practical difference whether the inheritance comes from the mother or the father.
The first difference - the inheritance of the firstborn:
A firstborn son, meaning the one who is born first among the children and is a male, takes a double portion - a double share - only when he inherits from his father. Two brothers who are the sole heirs to their father: the firstborn takes two-thirds, and the younger takes one-third. However, this law applies specifically to the inheritance from the father.
If the mother outlived her husband - and we must remember that when a woman passes away, the first to inherit her is her husband, and in the absence of a husband the first natural heirs are her children - the two sons will inherit equally, half and half, even though one of them is a firstborn.
It is worth mentioning, since we always focus on the father's family tree, that if the father had several wives and several families, the firstborn is the first male born to that man. Even if there were ten families, only in one of them could there be a firstborn - the son born first to the father.
The second difference - the support of daughters:
"Habanos" - simply put, the daughters are supported from the father's estate and are not supported from the mother's estate. However, this wording is slightly misleading, because this is not a law of inheritance per se, but rather a separate Rabbinic law: one of the conditions of the kesubah is that the man who marries a woman obligates himself to support her, and not only her, but her daughters as well are supported from the estate prior to his heirs, as long as the daughters are minors - until the age of twelve - and are unmarried.
This is therefore a contractual obligation that the Sages instituted in order to protect young daughters. The practical outcome: if there is not enough money in the estate to distribute to everyone, all the money is prioritized for the support of the unmarried minor daughters, before the heirs - the sons.
In summary: These are the two differences between inheritance from the father and inheritance from the mother - the taking of a double portion for the firstborn, which applies only to the father's estate, and the support of the daughters, which is collected only from the father's estate.
At the beginning of the ninth chapter, we will expand on the law of the daughters' support and its details.