Midrash su Genesi 46:15

Abba Chalipa Cruyah questioned R. Chiya b. Abba: "Of Jacob's children who came to Egypt in the total sum, you will find only sixty-nine." And he answered: "There was a twin with Dinah, as it is written (Ib. 46, 15) V'eth (with) Dinah their sister." According to your theory there (Ib. b) was a twin with Benjamin also, for it is also written (Ib. 43) Eth Benjamin. Whereupon R. Chiya said: "A valuable pearl was in my hand, and you wanted to deprive me of it? So said R. Chama b. Chaninah: 'This refers to Jochebed, whose mother was pregnant, and bore her within the walls, as it is said (Num. 26, 59) Whom her mother bore to Levi in Egypt; i.e., she was born in Egypt, but her pregnancy was not in Egypt.'"

Jacob heard this word, and he took his wives, and his sons, and his daughters, and the daughters of his sons. Another Scripture says, "With his daughter Dinah" (Gen 46:15). And all that he had, and he brought them to Egypt, as it is said, "His sons, and his sons' sons || with him," etc. (Gen 46:7). Another Scripture says, "With his daughter, Dinah" (Gen 46:15). Whereas another text says, "His daughters" (Gen 46:7), to teach thee that the daughters of Jacob were the wives of his sons. And all the seed of Jacob married their sisters and their blood-relations, so that they should not intermarry with the people of the lands, therefore they were called a true seed, as it is said, "Yet I had planted thee a noble vine, wholly a true seed" (Jer. 2:21).