Hello,
My wife came with Guinea pigs. When we moved in to this house, the 2 pigs (one of each) were relocated from when she lived. They were an essential consideration in whether the house was right! We then rehomed 2 males about a year ago, but one started humping the other, before Christmas, so we separated them. Apparently it's a dominance thing, Had one castrated to allow them back together, but complications set in and after more surgery, we lost him. Castration does nothing to change behaviour, just stops them having babies.
So we tried boar-dating and thought we got a match, took him home but a little later they weren't getting on. So separate cages again... Then we lost the original female - from old age (she was 7 1/2).
So now we've 3 males.