Welcome to Pettalk! Spencer has the most personal experience with this, so his good advice is worth listening too, Logan and others I know can offer great insight as well.

One thing I would add is that they are both "acting normal". Cats have individual personalities like people do.

I would agree with Karen that they are battling for "top cat" status around the house - cats are territorial by nature. Is there any way you can find out the "past lives" of your fur babies?

Some behavior may be a result of past treatment. Patience and a loving, trusting environment can do wonders, though - good luck! Would love to see pictures of your adopted kitties!