Another thing I find interesting is that your family right now are the most closest humans related to you. When you go back in time or forward in time, the relatedness dilutes.
That would be impossible, unless one of you is some kind of bacteria. And even in that case I doubt it. According to Wikipedia[1] (yes, I invested some time to refute a random stranger on the internet, well, maybe a cousin) there is something like 0.1-0.4% of genetic variation between humans.
So yes, statistically one could with probability of something like 1/(2^30000) receive a complete different set of genes than a sibling. In the real world, one will always share around 50% of ones genes with a sibling.