Since Ukitake becomes the right hand of the soul king and fuses himself with Mimihagi, will Ukitake's soul be affected after Yhwach absorbs the soul king?
The specifics of what happened are not clear, but what is clear is simple.
Warning heavy spoilers ahead, because the anime has stopped before the latest arc Thousand Year Blood War.
In chapter 620, Yhwatch proclaims he will take everything that was the soul kings, including the right arm. IN chapter 621, we witness Mimihagi, the soul kings right arm, separate from Ukitake and he is left unconscious on the ground. Therefore, though it is speculation, it is probably a safe assumption that the Mimihagi was absorbed, while Ukitake was left alone and not absorbed. A Shinigami's Body is their soul, and even though Ukitake combined with it, it still separated from him fairly easily. We also know one more thing, A few chapters earlier, shortly before Mimihagi stabilized the soul king, Ukitake stated he should have died when he was 3, were it not for Mimihagi inhabiting his body, and halting the lung disease he suffered. With it gone, he is no doubt completely incapacitated, and probably not far from death unless one of the scientists of the Gotei can heal him, if not dead already.
And now, As of the end of the manga, Ukitake's fate was revealed:
After separating from the right hand of the soul king and being left unconscious, he died. As shown in the 2nd to last chapter in the manga, 685, Shunshi was visiting his grave.
Yhwach has only absorbed that part of the soul which was in the crystal . when you read bleach 612 manga , you see that in the crystal the soul king doesnt really have his left or right hand . so we could say since the soul king doesnt have either of the hands to begin with it is not possible that he absorbed ukitake and mimihagi.
I do not think Ukitake's soul will be affected by Yhwach. As we have seen that Soul King's right hand absorbs the soul of Ukitake completely and that is the end to Ukitake. Yhwach absorbing the soul king is complately different and has nothing to do with Ukitake's soul