
1. You're saving two lives instead of one.
By taking home two, one more kitten gets a home instead of growing up at the shelter. Kittens are much easier to place into homes than adult cats. If all the kittens are adopted quickly, then the older cats have a better chance of finding homes.
2. One kitten can become lonely.
A kitten left alone can become lonely, bored and get into mischief. Two kittens will keep each other company and play together. Siblings and cage-mates also can form close bonds while in the shelter and will benefit from going home together.
3. One kitten can drive an older cat nuts.
An older, established cat will likely accept two kittens better than one. Instead of a single kitten who wants to play or pester the older cat. Two kittens will play together and leave the older cat alone.
4. Two kittens will "self-train".
Kittens learn by copying. If one kitten has developed appropriate litter box use, the other will be likely to copy. They also will help each other with grooming.
5. They help each other burn off energy.
Even the most exuberant cat owner can get exhausted trying to keep up with the energy of a single kitten. Two kittens will wear each other out, so you are free to enjoy watching them play.
6. There are fewer behavioral problems with two kittens.
Many people who experience behavior problems with one kitten find that many issues go away with the addition of a playmate. Their 'bad behavior' is often the result of boredom, also negative attention is better than no attention.
7. Curiosity gets the better of 'finicky eaters'.
If one kitten is finicky about food, their attitude is often overcome by curiosity at what their partner is eating. 
8. They act as pillows for each other.
There's no sight so endearing as two kittens curled up for a nap on each other after a long day of play.
9. They will each have a friend for life.
Two kittens who grow up together will almost always be lifelong pals. If you are adopting a kitten, please consider getting a second kitten. You won't be able to devote all of your time to a kitten and during the times you're away, two kittens will keep each other company.
10. Having two kittens is twice the fun.
There is no denying it, kittens are great. Having two is definitely better than one!