I have so far always sold in at least pairs, although one is going this week she is joining a small flock that had two of mine a couple of months ago. I bought a pair of lambs and a single earlier this year and while they all graze together (12 in total) the single still tends to graze alone, but only a few foot away and less and less over time, the pair as a pair and the more established ones on recollection all took several months to forget the early allegiances. If they are feeding then a hand ful separate to the others may help in the early days.