I have two cats, a 1 year old male about 12lbs and an 8 mth old female about 9 lbs both about the same length. We've had one about 8 mths and the other about 2 months. Mostly they get along fine but between last night and this morning I have seperated them at least 4 times because one or the other started hissing and ears started going back. I'm not alway sure why their play goes wrong. I know sometimes one wants to play and the other doesn't, but this morning my male, Eclipse, just kept going after Fluffy and I didn't see any reason for it. He didn't even look like he wanted to play. Any thoughts?