Q. Did Jacob and Esau have siblings? When Isaac blesses Jacob (thinking that he is blessing Esau), he says, “Be lord over your brothers, and may the sons of your mother bow down to you.” This leads me to believe there were siblings, even though they are not mentioned anywhere else in the story.
This is a very perceptive question. I have to admit that even thoudh I’d read this episode many times before, I never noticed the issue.
I think it is unlikely that there were siblings. We learn earlier in Genesis that for a long time Isaac and Rebekah were unable to have children. Isaac was forty years old when he married Rebekah, but he was sixty years old when Esau and Jacob were born, after “Isaac prayed to the Lord on behalf of his wife,” and “the Lord answered his prayer.” (As a side note, I don’t think Isaac waited twenty years before he started praying for Rebekah. Rather, I think this is an example of someone who persevered in prayer over a long time and finally had his request granted. It illustrates, as Jesus said, that we should continue in prayer and not give up.) But given these circumstances, it does seem unlikely that Isaac and Rebekah had further children, and indeed the Bible doesn’t describe them having any more.
So what, then, does Isaac mean by “your brothers” and “the sons of your mother”? Interpreters who do address the issue tend to take these phrases as referring to all related tribes. Ellicott says in his commentary, for example, that they would “include all nations sprung from Abraham, and all possible offshoots from Isaac’s own descendants” (in other words, all of the tribes and clans that eventually came from Esau). Keil and Delitzsch observe that Isaac’s entire blessing first envisions present agricultural prosperity (“an abundance of grain and new wine“), but it then looks forward to the “future pre-eminence of his son”: not only over “kindred tribes,” but also over foreign “nations and peoples.” In fact, “The blessing rises to the idea of universal dominion, which was to be realized in the fact that, according to the attitude assumed by the people towards him as their lord, it would secure to them either a blessing or a curse.”
Ironically, Isaac doesn’t realize that he is conferring all of these blessings on Jacob rather than Esau. But as events unfold and God works out His plan through the choices, good and bad, of human moral agents, Jacob becomes a transformed man, he is renamed Israel, and he becomes the ancestor of Jesus the Messiah. As a result, as Paul writes in Galatians, “the blessing given to Abraham” (and repeated to Isaac, and passed on here by Isaac to Jacob) “came to the Gentiles through Christ Jesus.” And so it is no longer a matter of being one of Jacob’s “brethren” (a member of a kindred tribe), but of assuming an attitude of loyalty and obedience to his greatest descendant Jesus as Lord, that enables a person to share in the blessings that are embodied in Isaac’s words.
Good Question 
I would like to know what you think about what’s going on in our world today. And do you think that the Bible is fulfilling itself today in 2020? Are do you even believe that God is coming back, and the book of Revelations must be fulfilled before God’s returns? I would like to know your thoughts on this matter.
Jesus himself said of his return, “But of that day and hour no one knows, not even the angels of heaven, but My Father only.” So I would hesitate to declare too confidently that prophecies are being fulfilled this very year that would lead to Christ’s return. Instead, as Jesus told his disciples when he said this, we want to make sure that when our Lord does return, he finds us doing the work he has entrusted to us. So whether Christ returns soon, as I hope and pray for, or whether that will not be for some time, we need to be about our Lord’s work. And that work is, as Jesus himself once again put it, “to bind up the brokenhearted, to proclaim freedom for the captives and release from darkness for the prisoners, to comfort all who mourn.” May the Lord find us doing this whenever he returns.