I've stated this before in other threads, for probably the last 7-8 years but apparently it's not being referenced...........
I you want a pair you have to buy a group(at least 4) & let them sort it out on their own. It's easier to keep 4-6 than it is 2-3.
Groups can be kept & it's best to keep them in a species tank or just a few small dither fish. They get more aggressive with more competition for food.
Pairs will swim in proximity, but groups won't............they are basically all over the tank.
I've kept 4/5 together and pairs. Sometimes you can get lucky & two random one's will pair up. I've never tried pairing up just two from the ocean.
They were two from different tanks, so they were "domesticated" for a few years & mature.
They may pair up when small, but when they mature, if they aren't male/female it won't work. They are easier to pair up when older or more mature.
When I used to get them, larger ones were common...........today they are always small & probably not mature, so I think that's why some pairs break up.
They grow very slow if not at all............they aren't going to get dinner plate size.............so they aren't out of reach for most tanks but you still have to be smart & don't crowd them in a heavy populated tank.
New ones need to be Qt'd, they are hardy to adapt & eat, but they are very suseptible to diseases & bacterial infections.
Those are my experiences over the years, but the main thing is concerning the pairing & grouping. If you aren't prepared to buy more than 2 or don't have somewhere to keep the one or two that need to be removed then don't buy them.
I would follow those pairing rules with all BF's..........buy more than two & be prepared they may break up if not mature.
I'm sure someone will post how they bought a pair & they have been great the whole time. I say you got lucky that they were compatible, but the odds are against that working ---33% success at best.