I'm gonna tell you what I understood:
Ohana was Shunsui's brother's wife;
She left her zanpakuto (that in her family is passed on) to him;
Nanao didn't possess a zanpakuto (if you whatch closely, she NEVER have one at herside), or she was probably only using a regular sword;
The 2 "Zanpakuto's girls" are Shunsui's Zampakutos;
One of the 2 (the young one) had hidden ('cause she likes to "hide" things), for the Whole time, the Zanpakuto that was supposed to go to Nanao (at her mother's death).
Rukia didnt have her bankai til recently and she was a vice captain, the bankai is a requirement for captains
Rukia was not Ukitake's Lieutenant until we see her with the lieutenant bage in the full-bringer arc. There was no lieutenant after Kaien. The two third seats Kiyone and sentaro helped with duties but they were not lieutenants. Rukia had her shikai and we did not see her bankai until just recently.
You have to have a bankai to be a lieutenant. Example: Rukia complemented Renji for his new rank when he visited her in prison in the soul society arc. He was not Byakuya's lieutenant until then.
Was a bit convoluted. Ohana was the brother's wife and she left the sword to Shunsui. So Nanao was using a regular sword and not a zanpakuto the whole time? And those 2 zanpakuto girls, one blade is Shunsui's and the other is Her's from the other sword? But, the other sword was hidden in the young girl zanpakuto? I'm confused cuz he clearly fought with two swords. Sigh, make more sense, Kubo!