If a man has two wives, the one beloved and the one hated, and they bear him sons, the beloved and the hated, and the firstborn son is the hated one’s—
English: “And they bear him” — to exclude the case of doubtful paternity (whether a nine-month child of the first husband or a seven-month child of the second).
On the daf / in context: When a woman remarries too soon and bears a child of ambiguous gestation, the child inherits from neither possible father. The same exclusion applies to the bechorah calculation.
Type of Learning
Mi’ut from “ve-yaledu lo” excluding cases of safek.
What Is Learned
A child of doubtful paternity does not inherit the double portion (nor ordinary inheritance) from either possible father.