Dear little souls, well done.  And although the male won´t mind, often the less favourite female is a little neglected.
For example, I bought a trio, and after keeping them in a trio for 2 seasons, I can definitely say that the undergoose needs her own mate, as the favourite goose is the one that gets help from the gander with the babies, whereas the undergoose gets her babies stolen from her by the favourite goose.  The gander was actually taking the goslings from the mum to his favourite.  
I also had another gander with 3 almost inseperable sister geese.  He has his favourite, but mated with the others.  I let him stay with his favourite, but when the eggs of one of the other geese didn´t hatch, yet the eggs of the third did, those two geese set up family to raise the 4 that hatched, behaved like a pair, and were very happy like that raising 'their' brood.   And the gander was happy with his favourite goose and his little family of 7 goslings.  They´ve become one flock, now, as the 3 sisters have a very strong bond, and the gander just tags on behind with his precious babies (they´re huge!) 

   This year they´ll all have their own gander.
So, after all that, geese in pairs are ideal, although a trio is ok.