If your cage is at least 7.5 square feet, you may be in a good position to give your pig a buddy.
Be sure to try and find a local rescue to help with dating since not all pigs will automatically like each other, and you'll end up with two separate cages of guinea pigs if that's the case. Any pigs coming from municipal shelters or craigslist, etc, will need to be quarantined for a full month before introductions, and pre-emptively treating them for mites at the same time isn't a bad idea!
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