I didn't start any of my businesses with my brother or sister, but I did bring my brother-in-law into my first business when it was still very young. We didn't get along, and I wound up firing him. My sister didn't speak to me for the next 20 years.
I know a lot of entrepreneurs who could tell you similar stories, but I'm not suggesting that you should never start a business with a sibling or other close relative. I know people who've done it and have no regrets. Before you try it, however, you need to think hard about the risk you're taking. Splitting up with a sibling business partner is not like splitting up with a partner whom you never have to see again. These breakups affect both your business and your personal life. I have a friend whose two brothers recently fired him from their custom jewelry business. It's awful to watch the emotional pain they're going through right now, and there's no telling when, if ever, it will end.
Some people would argue that because you know a sibling so well, there's a better chance the partnership will work out. That may be true, but building a business puts stress on a sibling relationship that wouldn't occur in a purely business relationship. That's because business reveals unknown aspects of a partner's character--traits you might not like. That's what happened with my brother-in-law and me. I found him overbearing. He found me bullheaded. Once I decided we could not co-exist in the same company, it was too late to prevent damage to the family.
Some sibling partnerships work, and many have produced great businesses. But I'm sure just as many sibling partnerships have ended in a failed business and family bitterness. On the basis of my experience, I recommend avoiding it if you can.