Genesis 25-26

25:6 sons of the concubine? He didn't consider them sons?

Gen 25:6  But unto the sons of the concubines, which Abraham had, Abraham gave gifts, and sent them away from Isaac his son, while he yet lived, eastward, unto the east country.

Keil and Delitzsch commentary:  "Abraham's Marriage to Keturah is generally supposed to have taken place after Sarah's death, and his power to beget six sons at so advanced an age is attributed to the fact, that the Almighty had endowed him with new vital and reproductive energy for begetting the son of the promise. But there is no firm ground for this assumption; as it is not stated anywhere, that Abraham did not take Keturah as his wife till after Sarah's death. It is merely an inference drawn from the fact, that it is not mentioned till afterwards; and it is taken for granted that the history is written in strictly chronological order. But this supposition is precarious, and is not in harmony with the statement, that Abraham sent away the sons of the concubines with gifts during his own lifetime; for in the case supposed, the youngest of Keturah's sons would not have been more than twenty-five or thirty years old at Abraham's death; and in those days, when marriages were not generally contracted before the fortieth year, this seems too young for them to have been sent away from their father's house. This difficulty, however, is not decisive. Nor does the fact that Keturah is called a concubine in Gen_25:6, and 1Ch_1:32, necessarily show that she was contemporary with Sarah, but may be explained on the ground that Abraham did not place her on the same footing as Sarah, his sole wife, the mother of the promised seed. Of the sons and grandsons of Keturah, who are mentioned in 1Ch_1:32 as well as here, a few of the names may still be found among the Arabian tribes, but in most instances the attempt to trace them is very questionable."

Well, trip my trigger.  I'd always seen Genesis as pretty much a chronological retelling.

25:22 Rebekah went where to inquire of the Lord?

Gen 25:22  And the children struggled together within her; and she said, If it be so, why am I thus? And she went to enquire of the LORD.

Matthew Henry's Concise Commentary: "Isaac seems not to have been much tried, but to have spent his days in quietness. Jacob and Esau were prayed for; their parents, after being long childless, obtained them by prayer. The fulfilment of God's promise is always sure, yet it is often slow. The faith of believers is tried, their patience exercised, and mercies long waited for are more welcome when they come. Isaac and Rebekah kept in view the promise of all nations being blessed in their posterity, therefore were not only desirous of children, but anxious concerning every thing which seemed to mark their future character. In all our doubts we should inquire of the Lord by prayer. In many of our conflicts with sin and temptation, we may adopt Rebekah's words, “If it be so, why am I thus?” If a child of God, why so careless or carnal? If not a child of God, why so afraid of, or so burdened with sin?"

Eh...sound advice, specifically, "The fulfilment of God's promise is always sure, yet it is often slow."

Patience and long suffering, waiting upon the Lord.  *sigh*

Gen 25:23  And the LORD said unto her, Two nations are in thy womb, and two manner of people shall be separated from thy bowels; and the one people shall be stronger than the other people; and the elder shall serve the younger. 

So was Rebekah 'backing' the winner in making Jacob her favorite?