A male ane female "playing" together, even where you can see, will still make a litter. If your parents won't take a sick guinea pig to the vet, the last thing you need is a pregnant guinea pig which may require emergency attention.
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