Are siblings important?

I have the most precious 15 month old son ( a little biased but that's a mother's right, isn't it?). My husband and I were reluctant parents, meaning we weren't sure we wanted children. Although I married at the age of 32, it was a good 4 years before I realised that I did want children and the near impossible task of getting my husband aboard. Anyhow, finally 5 years into our marriage, we were blessed with our son. As it was a concious decision, we were aware of how much work it would be, what we were pleasantly surprised with was how extremely joyful this journey of ours was. I truly never expected it to be this much fun. Most people will be surprised at my comment because its obvious but for us it wasn't. We were unaware of the pleasure of seeing a tiny baby, day by day becoming a little boy.
Now, stage two, I feel siblings are important. No matter what your relationship with your sibling is, they truly define you as an adult. If the age gap between siblings is not too much, they become your playmates during your childhood years. As adults, siblings are the one ones whom  you can truly share your memories and feelings about your parents, grandparents and childhood. And I also believe biology is so strong that the one who can truly understand what you are going through when you lose a parent, is your sibling. Whether its pain, confusion or even anger, your sibling will be the best chance to having someone truly understand your feelings.
Now, the opposite view which my husband takes is that as parents one can spend more time and money on a single child. As adults sometimes, the maximum disappointment & pain comes from siblings. Also, in today's scenario where relationships are being redefined, our friends are taking on the roles of family. So, why go through the 'bother' of having a second child?


My very personal viewpoint  is this.
When I see my very young baby boy looking with excitement at other children, I think his need for company is going to grow. As parents with a 35 year age gap with our children, we can only physically run around with him so much and no more. Also, as he gets older, will we be able to truly see eye to eye with him on his ideas and philosophies, even if one tries to be open minded, the age gap is huge. And in my observation, most single children are selfish and self absorbed. They not only have a harder time sharing as children, but when they enter marriages or such relationships, they are less giving. Professionally also, they tend to be more ruthless. Of course, this is only my personal point of view, and not at all an academic or professional observation. (DISCLAIMER!!)

SO:
What is your personal opinion?
Are Siblings important?
Please tell me................