Well, I’m an identical twin and, oddly, I have identical twin first cousins. I say oddly because identical twins aren’t thought to run in families (in contrast to the maternal transmission of fraternal twins owing to greater numbers of eggs released). Most scientists think that identical twins are a random event. With an incidence of 1:300 births (speaking of identical twins), having two sets in the same extended family would be rare but not mathematically impossible.
With all that prelude, its hard to answer your question. I’ve always been a twin, and so I cannot envision life without being a twin.