yes
First of all you spelled hurt wrong, i changed it. But every animal gets hurt, dogs cats, lions , and many other animals. So yeah every animal.
When cats play, they may engage in gentle mouthing behavior that looks like biting, but they are not actually trying to cause harm. This behavior is a way for cats to playfully interact with each other and practice hunting skills without causing injury.
Cats can fight because they are territorial and do not want other cats to intrude. They can also fight over food, water and attention. It can take awhile for cats to become friendlier with each other.
Cats recognize each other be scent, so cats often go right up to each other and sniff each other when they meet. If the two cats like each other, often they will rub their cheeks together as well.
They lick each other
If they're newly adopted, you might want to introduce them slowly, getting their scents on towels and letting the cats smell each other without physically meeting. If both cats are neutered/spayed, the cats will most likely get along better, as fertile cats tend to be more defensive. My two cats have about a ten year age difference and they still spat occasionally. They are both male. So that they don't hurt each other if they do fight, try buying nail caps (some can be found at www.softpaws.com) for them. These can be glued to the nails and don't hurt them at all. Many times, what looks like rough fighting can actually be playing. Our cats like to pounce on each other and startle each other. However, if either of your cats do injure each other, keep them separate as much as possible. See a vet for more solutions; they are trained professionals and can probably help you more than I can. Thanks!
It could be they are lonely or getting hurt by other cats. Or they could possibly be somewhere hurt or badly ill.
when the cats are near each other the fleas jump to the other cat =]
well obviously!!
Siamese cats can be very mean at times to other animals but if you are with them they will probably not harm your puppy.
by drinking each others milk
Because birds understand each other better because they are the same species. It's a bit like cats and dogs. They don't understand each other but cats do understand other cats.