odd behaviour

Question
I have a female dog called Jas. This morning my mum brought home a big bed for Jas and my other boxer dog DJ, but Jas just lays on the bed all the time, and when DJ tries to go on it Jas gets aggressive this is also the case when we go to touch the bed she shows her teeth and growls, she's normally a playful loving dog, but she's acting very strange. We thought that with having DJ and Jas in the same room over night that he could of got her pregnant with her acting like this, but there brother and sister so would that be a problem? She's not big around her belly but we are concerned could you help please.

Answer
First, let me address the incest breeding............you CANNOT breed brother and sister- you will get deformed puppies- most likely clef pallets. DO NO ALLOW BREEDING.......... Get them neutered and spayed. Be responsible.

Secondly, not all dogs want to share their sleeping areas- get another bed for him so she can have her own.