I recently (yesterday) introduced a new kitten (11 weeks, male) into the household where I have one kitten already (5 months, male). I went through some of the standard introduction techniques and once the hissing/growling stopped I allowed them some face time.
The new kitten is blood related to the older one and was living with other cats, the older kitten has been alone for 3 months (with a brief visit to relatives where he stayed with two adult male cats for 10 days and got along fine with them after 2 days).
The older kitten chases the little one and then jumps on him, biting his neck and stomach. The little one growls/meows and cries, but usually does fight back. The older one does not back off when the little one cries. My concern is that the older kitten continues to do this when they are together. I can't tell if it is play fighting/dominance stuff, or if I should separate them and slow down the introduction process.
They do relax together sometimes (within 5 feet of each other) but I'm always in the room. I'm afraid to leave them alone together for fear that the little kitten will be bullied non-stop.
Any advice or insight to put my mind at ease would be appreciated.
Also, they are both getting neutered in 3 days.
the introduction process should really be carried out over a period of a week and done in a safe environment where the cats can get to know each other without the fear of injury.
i have a web page which describes the process in full
When cats do play it can look quite rough but generally they should not cry out as there should be no pain involved. once the kittens are more comfortable with each other the aggression should stop. I would also recommend if you have not already done so, have the 5 month old male kitten neutered soon, as this too can cause aggression and friction.
best wishes Kate