Both Smooth and Wire Fox Terriers love people but were bred to hunt other creatures.  Some have a strong "prey drive", which means that they don't think about it, they just go after other animals. Many others don't have that strong a prey drive and they can live peacefully with some other small pets.

If you have other pets in the house, you should consider the temperament of the fox terrier before buying one or adopting one.  Getting a puppy will not make any difference, as this behavior is bred into them and cannot be "trained" out. 

Some will be fine with other house pets, such as a cat, but outside they will go after the cat.  Same with birds, if you have a pet bird and it is allowed out of the cage, I would certainly not have a fox terrier.  It's just asking for trouble and a fox terrier can take a bird out, by jumping and getting it in flight.  Don't take the chance with the birds life.  Small pets like hamsters and pet mice and rats, and guinnea pigs or pet rabbits, these are all seen as "food" and will be attacked and killed by most fox terriers.  They will be proud of the kill and may bring you the body.  This is horrible for a child to see, and it's not the fox terriers fault, he is doing what he was bred to do.  Most likely the fox terrier is not for a family with other small pets.

Fox Terriers can get along with other dogs, but you have to be careful.  They can see a toy breed as prey too, or just playing with one can hurt or kill it.  Not being mean, they just play rough.  They will also take on a larger dog, a much larger dog, as they have no fear.  So you must be very careful.  We find that if the males are neutered and hopefully by six months, they are not as aggressive.  But the females just don't get along.  We strongly suggest that you never try and put a female fox terrier with another female dog, especially another female terrier.  They can fight to the death. 

Meanwhile, they love people and it's rare that a Smooth or Wire will bite a human.  However, they will sometimes protect a toy or food, and if you try and take it away, you could be biten.  Gentle training to "give" helps to let the dog know that you are not being aggressive towards them, but that they must give you the toy/food.  If you train this very early in life, it will save you from many problems later.  Never be harsh or loud, a soft voice will get you much further.

Just be very careful if you are picking a Wire or Smooth to live in your family if you have other pets.  Always have your fox terrier on a leash when he is out of your house/yard.  They will go after another animal and like a small child, not look where they are going.  Be safe.