Join Date: Mar 2010
Location: Ontario, Canada
Whether or not you should have one cat or two depends on whether you prefer one or two, and whether you have the necessary time and financial resources for one or two. Most Ragdolls, like most cats, can typically be happy as either an only cat or with another cat (particularly if the new cat is adopted when both are at a very young age).
If you do decide to get a second cat, then you could get another Ragdoll or any other breed of cat. The most important thing when getting a second cat is to try to match the personality of the first cat. So, if the first cat is shy, get another shy cat (of any breed). If the first cat is active, get another active cat (again breed doesn't matter).
Finally, if you're going to adopt two kittens at the same time, then two littermates would normally get along very well. But, two kittens not from the same litter adopted at the same time will typically also get along pretty easily too, assuming they're both very young when you adopt them. You should ensure that both kittens are spayed/neutered as soon as possible, particularly if one is a boy and one is a girl. Even if they're brother and sister, they will mate when their "time comes".
In short, you should really think about what you want. Do you want a second cat? And, if so, would you like two Ragdolls or one Ragdoll and one cat of another breed? Your Ragdoll will likely be happy either way...particularly if you adopt two young kittens at the same time.