In my case we just didn't have the chance to have enough Tower people around us so we can perform the first siblings ceremony that's why for now just near brother and sister *sigh*
Since it isn't an official relationship that is recognized by the Tower, I don't see why there would be any official rules/regulations other than the guidelines provided in the Library. I say you just do it, but that's just my opinion. :tug
I agree. If you have one witness, or two, or none, you can still speak the words and do the slapping. Improvise.
One first sister ceremony I saw had one of the ladies' mother on the phone, talking over the phone. My husband and his first brother Soro had one person there as a witness. Greens tend to slap twice as in the books rather than once as in our 'official' ceremony. Another pair of sisters I know did it completely privately, just the two of them. There's no right or wrong way to do it, except depending on your desires for the ceremony.