There are many articles on the internet regarding "Having 2 kittens (or cats) are better than having just 1!! Here are links to a few of our favorites:

http://cats.about.com/od/wheretoadoptacat/ss/twokittens.htm

http://www.companionanimalpsychology.com/2012/06/one-kitten-or-two.html

http://www.catbehaviorassociates.com/adopting-a-kitten-make-it-a-double/

http://www.catster.com/lifestyle/cat-behavior-care-adoption-tips-two-multiple-cats-better-than-one