Let's see...after getting my first chi, I got the second one about a year later. But then about 6 months later I got litter sisters. Two were great-they played together and slept together...did not have separation anxiety. It has been two years and in May I purchase a little male puppy-8 weeks old and at the end of May I purchase a little female puppy-6 weeks old. The female had separation anxiety-bad-howled all night until she started sleeping with the other puppy. They are now together all the time. They play well together, even though they have 7 weeks between them. I just made sure to watch them during the time they were together for awhile. Did not want the male dominating because he was larger. But she did not let him and they are now great playmates. Yes, if you count them, I have 6 chis.
I do not put the puppies in the same area as the adult dogs when I am gone. I have read horror stories about that. And 4 adult dogs are nothing against a puppy.