I think it is important to have siblings, just because it helps to teach you things in life that you may not otherwise be able to do if you are an only child. For example, learning to get on with a person of a similar age, learning to live with someone of a similar age, etc, which are good skills that could help you later in life. It also teaches you to be able to share and get on with someone, and in the future it will be nice to have someone around once your parents have gone to share memories and experiences with.