I currently have just one, but had two up until last year. I have had up to I think 11 or 12 at one point between me, my sisters, and mom. I liked having two, but don't plan to get another until my current one passes do to his age and I really don't have room for a second cage. I will likely try to get another pair when the time comes, but if I had the room I would want more, maybe 4, I really did enjoy having a a small herd of chins growing up, they each have their own uniquely different personalities, but they were a lot of work. I think they benefited from having other chins around, especially when I was a kid since my mom worked and my sisters and I were in school all day. They were mostly all caged separately but in the same room, so they still could see and chat with each other and weren't all alone. We also did gender grouped play times, so they got to interact with each other even if they didn't seem to want to share a cage. I'm now home all day almost everyday, so my current chin I think is doing ok as an only chin and although I do think he misses his brother I don't really think he needs another chin since I can spend a lot of time with him.
I just have the one....and even that was more than I'd planned to have, haha.
That said, I adore my chin and would be open to potentially having more in the future. However, finding space for a second large cage set-up would be a challenge right now, so given there's no guarantee Margaret would accept a cage mate, I'll probably just stick to the one chin for the foreseeable future. Margaret is young and will hopefully be with me for many years to come. However, things change. If I ever move to a bigger place (unlikely given how crazy expensive housing is where I live, but I guess you never know), I'd definitely consider getting more. Or if I hear of another single or bonded pair/group in desperate need of a new home, I might be able to find the space to cram another cage in here somewhere. Necessity is, as they say, the mother of invention.
But at least for now, I have no plans to get more chins any time soon. I have a bunch of other animals as well and I work full-time, so I think I have enough on my plate for now.
I have two brothers, housed together. They sleep side by side maybe half the time, which tells me they need each other. However, they do fight on occasion (always the same: Chicco is chasing Chino all around the two floors). They don't ever fight over food or treats that I hand out to them. They have different personalities, for example Chicco does not really like being held while Chino does not mind that at all. I think they do need each other. Although I'm mostly working from home, and the twins are (sometimes) playing with them, we cannot replace the comfort that another Chin can give, if they get along.
I am happy with having two, although I wish they had a larger cage (three levels) - I actually am considering it (posted a question in the housing section).
I do sometimes worry about Margaret being lonely. I know chins are naturally herd animals....but at the same time, they don't always seem to want a companion. I grew up keeping rats, and one of the cardinal sins of keeping rats is to keep them alone, because they tend to get super depressed without at least one cage-mate, so a part of me still has that mentality. I know rats and chins are very different critters, but I still can't help but feel bad that Margaret doesn't have anyone to talk to, even in a separate cage.
I just try to spoil Margaret to make up for the fact that she's a lone chin. I try to spend as much time as I can with her (usually around 2 hours on weekdays, more on weekends), get her out for playtime every day, make sure she has plenty of toys and chews to keep her occupied and enriched when I'm not home, etc. She seems happy enough as far as I can tell, and she's become very bonded to me. Always runs to the door of her cage to greet me, hops into my arms as soon as I open the door, loves pets and scratches and will even tolerate some cuddles ....I'm also the only person she doesn't spray pee at, haha (well, at least not for a while, she did get me right in the face a few times earlier in our relationship).