We had Bunni for about 2.5 years before we got Rikki. There were many reasons for adding another pug to our family, and high on the list was getting Bunni a companion so they could play with each other and not miss us too much when we weren't home (not that we leave the apartment that much).
Bunni and Rikki are actually littermates, but the breeder held onto Rikki for a while. When she became available last December, we snatched her up.
Any visions I had of Rikki and Bunni greeting each other with joy and recognition of a long-lost sibling were quickly smothered when I first met Rikki at the airport (I went to pick her up by myself). She was beyond scared and nervous, visibly shaking (we're talking petit mal seizure), and continued for a few hours until she basically passed out from exhaustion. This was not going to be an outgoing pug ready to embrace her new home and a reunion with her sister. I would have given her back to the breeder out of pity for Rikki except that I had already forked over the moolah so Little Miss Nervous was coming home with me no matter what.
On the bright side, she was scared so shitless that she didn't make a fuss at all in the carrier or on the plane. She was paralyzed with terror. Nice. That's just what I wanted for her first memory of me.
When I brought her into the apartment, she completely ignored Bunni and darted around the apartment, trying to get familiar with her new surroundings--totally understandable. When she did finally take notice of Bunni, it was to growl at her. That did not go over well with me. (Bunni, on the other hand, didn't seem to care much.)
That first night we had her, I'll admit, I cried. I felt like we had made a mistake. The main reason we brought her home was that they could be friends and companions, and here Rikki was snarling at her sister. Her own flesh and blood. Plus, at that time, my first loyalty was to Bunni, my "first-born", and so my heart just broke for her. I felt like I had ruined things for her.
One time during the first few weeks of Rikki joining us, she snapped/snarled at Bunni when Bunni tried to join me on the couch. I immediately threw Rikki on her back (there are differing opinions as to whether putting the dog in this submissive pose works) and said "Don't you growl at my dog." Kevin looked at me with his eyes all wide, pointed at Rikki, and said in the most shocked and indignant voice, "Rikki's your dog, too". God that little runt had Kevin wrapped around her pinky toe the second she walked through the front door. But yes, I was definitely loyal to Bunni.
Things got slowly better, but it was definitely an adjustment, and kind of tough. I'm not talking about training and walking and cleaning up poop, but rather the emotional aspect. I almost felt like Rikki was an interloper, encroaching on our space. I would look at her and think "Who are you? And why don't you get how this family works?"
Nonetheless, after time, we all started acclimating to each other, and to my heart's joy, the pugs started playing with each other. The first time they played with each other, again, I practically cried, because it was all I ever wanted for them two.
Now it's a solid family unit. They're a little pair--they play with each other, follow each other's leads, and with increasing frequency I see moments like this, where Rikki will voluntarily go up to wherever Bunni is and plunk herself right up next to Bunni:
Rikki says: Bunni, you make such a good pillow
Bunni says: You make a good pillow too, little sister
United in their desire for treats
Together in surrender at not receiving treats
Then I saw the cutest thing the other day:
Rikki: I'm sleepy, aren't you sleepy?
Bunni: Yes, I'm sleepy, too. I'm always sleepy. Aren't you?
Rikki: Yes, me too.
You hold paws with me so I can fall asleep, okay?
Oh, my heart.