User blog comment:Xilinoc/Ch. 616 - Mimihagi-sama/@comment-493809-20150219222357

I wonder if the scattered parts of the Soul King have a relation to the Hogyoku. Below, Mohrpheus brought up the fact that Aizen took something from Rangiku - perhaps she had gone through something similar to Ukitake (though less severe), and had a portion of the Soul King's Power. Then that power could have been taken and used as a basis for his Hogyoku.

If that were true, and Urahara's Hogyoku was made in a similar fashion, then the combined version that Aizen used would have 2 parts of the Soul King's powers (perhaps the legs?)

My main reasoning is that it would make sense if the Soul King's power is what allows souls to have their wishes granted. Also, looking at the picture of the Hogyoku, the crystallization MIGHT be related.

It would also fit with the conversation Aizen and Urahara had, where it was suggested that both had seen the Soul King in some way.