I agree with Catherine, socialization is a must, but it depends on the personality of the individual dog.
When we had 4, they all slept on the bed together and ran together and rarely did we have any problems. We added a puppy and things were still going ok, just really crowded. However, one day our youngest girl decided she was all grown up and didn't want to be bossed around anymore by our 'wanna-be' alpha. Neither of them was a true alpha. We managed to defuse the situation, but a month later it happened again. The girls could never be together again. In fact, the tri developed a predjudice against all red girls after that! Both girls were terrific with people and with Basenji males and even with males and females of other breeds.
I had 2 intact males, brothers, who stayed together with absolutely no problem for almost 4 years until one went to another home. They even got along during season.
Terry