In addition, it's hugely dependent on the size of the cage they're in. Imagine trying to live in a bathroom with another person. You'd be sniping and yelling at them and probably fighting way more than if you were sharing a whole house together, right?
Pet store cages, overall, are way too tiny for two pigs to live in. I've seen even bestest friends get territorial and snippy in one of those litterboxes.
Make sure you've got at least 7.5 square feet for a pair of piggies, and more is always better! You cannot have a cage too big for a normal, healthy pig.
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry