I think any number greater than 1. I think they help each other through rough times ie: food competition, who's in front on the walks, who's in the lap, bed, has toys, blankies, pillows, who barks first at the noise, who can jump the highest, who gets their head in all the grocery bags first and finds the treats, who can get to the bathroom first when Mommie has to go without tripping her up so she pees her pants!, and who gets belted in the van first when we all go to Petsmart or the park, and who gets out the door, doggy door and gate first, and who gets back first, who can pee the most, group sniffs, group pees, group poops, group growls (once synchronized)...etc. Having one is just too easy! I don't know what to do with an empty hand?

I tried putting both hands on one leash but it only would go in one direction!