Assuming you are in a home where you are joint owners or are both residents in someone else's home, there is no legal mechanism. If you both reside in someone else's home (such as your parents), you would need to ask your parents to interfere.
In his sister's house, in his old room.
It could cause you not to get along with your sister. If you are having disagreements over the room, maybe talking to your sister about solutions would solve the problem. It could be that sharing the room is not the problem, but you and your sister are so different that you do not get along.
Carry her out of your room or if she's too heavy, push her out of your room.
The two metaphors in "As my sister ran into the room my brother said, Let's hide from her" are: The sister's entrance into the room is metaphorically portrayed as a chase or pursuit. The act of hiding from the sister is metaphorically likened to seeking refuge or avoiding confrontation.
put a bolt on it.
There is no law that says a brother of a certain age can not share a room with his sister.
metaphor
Your room is 'ta chambre', your sister's room is 'la chambre de ta soeur' in French.
Buy a NERF gun and keep it by your side
Sneak into her room and touch her
Not sure why you need it, but "sister's" is a possessive noun. So it would be a possession of a (a meaning one) sister. I wore my sister's shirt to school. (my sister has a shirt that I wore) Which is different from the possessive plural noun sisters': I went into my sisters' room. (meaning both of my sisters share a room, and I went into it)
yes!