The important question is, is Bugsy spayed? If she is not, you will need to get her spayed first, and wait 1-2 months while her hormones level out. If she is spayed, you still can’t just let them play together. If Bugsy has been a single for her whole life, and you let these two random buns into her space, she could very well lash out and become territorial and aggressive. Not to mention, you could even break the bond of the current two by doing that. The bonded pair will need at least 2 weeks to a month to settle in and get used to you and the environment. I suggest keeping them in a different room than Bugsy to start out, as it could stress out the pair or Bugsy to just have new roommates. After they have settled you will need to prebond for at least a month, and let them get used to each other’s scents. Switching the pair into Bugsy’s cage for a few days while Bugsy is in their cage. Changing litter boxes between the cages. After this, you can begin sessions on neutral territory. So territory that neither Bugsy nor the pair have ever been into. Start out with short 10 minute sessions, and move up based on their reactions. You can check out Siruis&Luna’s thread, as she is in the process of bonding a trio. But I must caution you, if you attempt a trio with the Bugsy and the bonded pair, you risk breaking up the existing pair if things don’t work out, leaving you with three single buns.