These are a nuclear bomb and a laser gun.
Those are my sister and my aunt.
No. They may be technically correct but they sound ugly to my ear.
Instead, I'd use:
These [things / weapons] are a nuclear bomb and a laser gun.
Those [people / women] are my sister and my aunt.
This is a nuclear bomb and a laser gun.
That is my sister and my aunt.
These are nuclear bombs. (of course)
Those are my sisters. (of course)
CJ