The most important thing is: how is your life. The more cats you have the more space (and litterboxes) you need (if the apartment is tiny it might ībe difficult for 2 cats). Cats -especially if they do not go outside- are very social people. They are not happy when they are alone too much.

If we have been away a weekend, the catsitter came 2 times per day for one hour. Nevertheless Filou and Tigris are "velcro cats" when we come home and follow us wherever we are. So we feel it is better to have 2. (If your cat has good company most of the day, she or he may not miss anybody.)

They met at 16 and 13 weeks. 3 days they ignored each other and I started to feel desparate. Next thing they started to fight but there was no time to be more desparate because after their fight they fell in sleep in the same basket and started to behave like twins..
Now they do not sleep together very often but it still happens.