Is soup broth a geneous mixture?

That depends on the broth. When Bones are boiled there is always some amount of blood, marrow and other small bits that float in the broth. The sae is true of vegetable broth pulp from the vegetable and bits skin will break of during skin and mix into the solution. If all of the bits are completely strained out of the broth then yes a broth would be a geneous mixture but generally there is some amount of "sediment" floating in it.