Joseph Telushkin, in Jewish Literacy, pointed out that even though the biblical law permits polygamy, the biblical narrative advises against it. Whenever a man in the Tanakh has two wives, it seems to be an unhappy marriage: one wife is beloved but infertile, and the other one is fertile but unloved. We’ve already seen this happen with Sarah and Hagar; a few weeks from now, we’ll see it with Rachel and Leah; in Nakh, Hannah (Samuel’s mother) and Peninah have the same situation (I Samuel 1:1–8).
Against this background, consider what Rebecca says when she meets Abraham’s steward (Genesis 24:24): “I am the daughter of Bethuel, the son that Milkah bore to Nachor.” Nachor not only had a wife, Milkah, but a concubine, Re’umah (22:24). Why did Rebecca want to make it clear who her grandmother was? The simple explanation is that by announcing that she was descended from Nachor through his wife and not through a concubine, her family would get the better part of his inheritance. But it’s also worth noting that Milkah gave Nachor eight children (22:10–23), while Re’umah gave him only four. Is there some dynamic going on between Nachor and Milkah that is being passed through to the grandchildren, making them particularly concerned with their status and property (perhaps because that’s all Milkah is getting from Nachor)?
At any rate, you don’t have to be Stuart Smalley to think that Rebecca is coming from a somewhat dysfunctional family. She certainly doesn’t waste any time getting away from it.