Siblings are a difficult part of growing up—even when you're an adult, you're going to be prone to troubles with them. But, during your developmental years, you're going to be constantly compared to them—both by yourself and others. This creates complex psychological interworking and can create complex disorders and issues. And this is just with normal siblings; I can't claim to have one myself, but I can only imagine that with twins, it's a lot harder. No longer are they only similar to you or…

Infertile? There are many ways to have a son or daughter that never involve pregnancy: you can adopt, you can foster, or you can steal your sister's baby before it's ever born...