Give me children, or else I die (Genesis 30:1)As we know, Rachel finally became pregnant with Joseph much later, after 11 other children were born. And we know that Joseph ended up being sold into Egypt, where he was used as the Lord’s instrument to store food that ultimately saved the house of Israel (and a whole bunch of other people) from being wiped out by starvation. He was raised up for that purpose.
Would this purpose have been fulfilled if he had been born around the same time as Reuben and been one of the oldest of Jacob’s children rather than among the youngest? Would there have been that tension between the brothers? Would he have been sold into Egypt? Probably not.
Did Rachel realize that not getting to have children yet (as painful as it was) would culminate in the temporal salvation of her whole family? There’s no way that she could have known without revelation (And we don't know whether she ever knew.)
Thinking about this has suggested to me that Heavenly Father has good reasons behind His timing of people’s births in families of His Saints and good reasons for birth order. He is planning out not just parents’ lives, but he’s also synchronizing the lives of the children so that they are born at the necessary time that will build up to the fulfilling of His purposes for the maximum development of all of His children. Yet he has to also consider the agency of His children and provide backup plans. Some people may choose to be extraordinarily faithful, while others choose to drift and procrastinate their repentance.
We know that timing in some things for some people seems ideal, and timing for other people seems to be all skiddly-wampus. We can’t know why probably until much later when we get to see the end from the beginning. All we can do is do our part and trust the Lord.