While looking up info for a different question, I saw that on the pasuk in Bereshit 43:32, Targum Yonatan translates the word "Ha'Ivrim" as "Yehudaee", while Onkelos translates it as "Ivraee". Is Targum Yonatan inferring that at some point only Yaakov and his descendants were considered "Ivrim", which I take to mean descendants of Ever, and not all of Ever's descendants (Bnei Keturah, Lavan, Yishmael, Esav, etc)? Or is there another explanation for the difference in translation?
The term HaIvrim does not mean the descendants of Ever but refers to the meaning assigned to Avraham. That is he was on one side (עבר אחד) while the rest of the world was on the other side.
As an example, this is explained by Rabbi Daniel Lapin
Which makes the oldest and most venerable name for Jews also significant and meaningful. The name Hebrew, as in “Abraham the Hebrew” is a loose transliteration of the Hebrew word, IVRI.
And the fugitive came and he told Abram the Hebrew… (Genesis 14:13)
IVRI means someone who has crossed over, usually a body of water.
And I took your father Abraham from the other side of the river, and led him throughout all the land of Canaan… (Joshua 24:3)
Abraham’s first act of obedience to God involved leaving his birthplace and crossing the Euphrates River.
Joseph in Egypt was referred to as a Hebrew.
Now it happened, when she saw that he had left his garment in her hand and had fled outside, that she called to the people of her house, and she spoke to them, saying, “Look! He brought us a Hebrew man to mock us. (Genesis 39:13-14)
Joseph had also crossed a river, the Nile on his way to Egypt.
Guess who else crossed water and is also called a Hebrew? That’s right, Jonah.
And they [the sailors] said to him, “Tell us now, because of whom has this evil befallen us? What is your work and whence do you come? What is your land, and from what people are you?”
And Jonah said to them, “I am a Hebrew, and I fear the Lord God of heaven, Who made the sea and the dry land.” (Jonah 1:8-9)