Actually ferrets love company and play well (if trained and handled properly) with other creatures. My sweet little boy ferret loves my chihuahua and plays with her all the time. He never bites her or anyone else because I handled him properly and disciplined him without ever having to spank him or anything.
To answer the question you were actually asking the best things you can do is get your babies vaccinated and examined regularly by a competent veterinarian who has knowledge in ferrets. They will need rabies and distemper vaccs. Make sure to brush them everyday, trim their nails every two weeks on average, and bathe them about once a month or only if they begin to smell too bad. Ferrets have a natural musk that I enjoy but not all do so be prepared for that. Clean their cages if not daily once a week (depending upon how messy they are). Make sure they have a healthy diet high in protein and that they have Taurine in their diets as well. They are carnivores, that means make sure they do not ingest fruits or veggies as they cannot digest them. They require at least 4 hours of play a day and DO NOT I repeat DO NOT just turn them loose in your house. So many ferrets injure themselves because people just turn them loose. Buy a playpen or ferret proof a room in your home. If you find that they nip or bite you, say "Ow!" in a high pitch voice. Gently scruff them if they act out. That's what I did with my snuggle bug and he never bites. If you do this consistently, it will take about 2 to 3 weeks for you to notice strong changes in their behavior. That's the basics but I suggest you do more extensive research to make sure ferrets are for you. They require a lot of your time and dedication but I can tell you it is very worth it! :)
My advice is that it is a bad idea to get two ferrets. There will be jealousy between them. I am not quite conveying the concept that these are vicious wild animals capable of killing or mutilating another child or a dog or pet. They can never be completely trusted, despite the fact they seem "cuddly". They require daily maintenance and that means every day until they die. Add up the hours. They are a danger to any visitior who has not been around them.
Thankyou but what I'm worried about is the sickness in ferrets. We don't have other pets living with us, we only had. And the youngest member in the house is 14. Any tips in preventing cancer like what I wrote above?
We had a ferret for fifteen years and enjoyed it greatly. However, we got it very, very young, and it "bonded" with our family. We took it outside and slept with it. Be advised these are extremely dangerous animals perfectly capable of killing a baby, or a hundred pound German Shepherd. Under no circumstances can they be poked or prodded by a child. Only because we bonded could we play a little bit "roughhouse".Our ferret attacked a visiting police dog and almost killed the dog (I would not have believed that had I not seen it). My advice is do not permit any children not in the household to handle or play with the animal.