Bava Basra, Chapter 8, Mishnah 3. This Mishnah deals with the daughters of Tzelofchad themselves. To understand its statements and basic points, we must first establish the family tree.
Three preliminary facts:
Tzelofchad: A man from the tribe of Menasheh who died in the wilderness. He was among those who left Egypt, and according to the Tanna before us, this entitled him to a portion in the Land of Israel. He had no sons, only five daughters - the daughters of Tzelofchad - and they are his heirs, as explicitly stated in the verse.
Chefer: Tzelofchad's father. He too was among those who left Egypt and was entitled to a portion in the Land of Israel, and he too died in the wilderness. Aside from Tzelofchad, he had at least one other son, and therefore his sons are his heirs; and since Tzelofchad is no longer alive, his daughters take his portion in the estate of Chefer.
The firstborn portion: The Mishnah will state explicitly that Tzelofchad was the firstborn, the first child. A father's firstborn male son takes a double portion. Therefore, if Chefer had only two sons, Tzelofchad would take two-thirds and his brother one-third, and these two-thirds pass equally to the five daughters.
It is worth clarifying one point: if a man first had a daughter and afterward two sons, the first son is not considered a firstborn in relation to his brothers. Since the first child was female, there is no firstborn here at all.
The text of the Mishnah:
In light of this, the Mishnah states simply: "Bnos Tzelofchad natlu shloshah chalakim banachalah" - the daughters of Tzelofchad took three portions in the inheritance. They took portions in the Land of Israel in three different ways:
"Chelek avihen shehayah im yotzei Mitzrayim" - the portion of their father who was with those who left Egypt. Tzelofchad left the land of Egypt, and this departure entitled him, according to this Tanna, to a portion in the Land of Israel. Since he does not receive it himself, his heirs receive it; and since he has no sons, the daughters take it.
"Vechelko im echav b'nichsei Chefer" - and his portion with his brothers in the estate of Chefer. The grandfather, Chefer, the father of Tzelofchad, also left Egypt and was entitled to a portion in the Land of Israel, and he too died in the wilderness. His sons inherit him, and among them are Tzelofchad and one or more brothers; therefore, the portion that was supposed to go to Tzelofchad passes to his daughters from the estate of Chefer.
"Veshehayah bechor" - and because he was a firstborn. Since Tzelofchad was the firstborn of Chefer's sons, he is entitled to a double portion, and therefore his daughters take two portions in Chefer's inheritance.
For illustration: if Chefer had three sons, Tzelofchad would take two-quarters, and each of the other two brothers one-quarter. And if he had only two sons - two-thirds for Tzelofchad and one-third for his brother.
In summary: In this Mishnah, we discussed the family tree of the daughters of Tzelofchad and the three portions they took in the inheritance: their father's portion as one of those who left Egypt, their father's portion in the estate of his father Chefer, and Tzelofchad's double portion as a firstborn.