The Great Schism
Before the arrival of humans, when Ursa Major was still a wild and free place, the elves lived there and did as they wished and lived their lives as a celebration of nature. The world was vast and fresh. It was normal for an elf to have a dozen or more brothers and sisters. In turn, these would have a dozen or more offspring, as was the custom in the eternal feywild from which they came. In those days, Ursa Major was as vast and abundant as the feywild, with room for all to enjoy the new realm of the gods. When the gods created new children and placed them in the world, the elves understood that Ursa Major was not their realm. They were visitors, caretakers, of this land created by the gods. It was their duty to guide the gods children toward their inheritance of this unique place amongst the cosmos.
The new races flourished on Ursa Major, in particular, the race of humans. Of all the races to follow, they above all were given a collection of gifts that allowed them to survive and grow in any environment. They possessed an ambition to not just survive but redefine their environment to best suit them. It wasn’t just a task they performed, but the very core of their nature. They had the ability to reshape what the gods created. Ironically, they were initially the least equipped for internal peace than any of the races of light. Was it not for elven intervention, humanity would have become extinct as the ancient tiefling and deva races fought over who would claim Ursa Major as their realm.
Seeing the success of the human race, many elf scholars considered them their true successors, the new caretakers of Ursa Major. The first Lord of Elves, High Lord Eladrin, began the call for The Return Home, to shape humans to be the benevolent caretakers of Ursa Major, so that the elves could leave Ursa Major for the new children of the gods.
This caused a great schism among the elf people. Many agreed with their king, that they should return to the feywild. However, many did not agree with their king. Elves too were children of gods. They are the older brothers to the other races of light. How could they abandon the others to fend for themselves and perhaps die when the elves could help them and protect them from the darkness, from the children of Yeenoghu, the gnolls, and Orcus, the orcs. Those who sided with the king returned home and called themselves the eladrin.
After the schism, the elves who remained on Ursa Major understood that they needed to make room for their fellow man. They chose forests to dwell in that would be nearby man. And they began the practice of limiting themselves to only two children so as not to strain the environment around them and to represent the dual nature of the circumstance of their race.