Future cliff notes: Paid $20 to an undergrad architecture student from a local car forum for advice on a critical load bearing portion of uncles house and second floor collapses when aunt takes her first bath upstairs.
I am not nor never was an architecture student, but there is a lot you are leaving out. Are all the areas of the house involved here contained within the original structure, or does this include some type of addition? If it is solely within an existing structure, is the attic supported only by the outer walls, or does it utilize interior load bearing walls that rest on the second floor (or in the case of a remodel, walls that may have continued through the first floor).
I think to get any kind of good answer on this someone would need to look at it in person, and that person should be a professional.