we share 99% of our genes with a chimpanzee

99% of our genes have a chimp equivalent and vice versa

95% of our genes with a random human

In 95% of something or other of their genome two random humans have the exact same allele. In the other 5% they are no more similar than a human and a chimp are in the 99% that are shared between the species.

and 50% of our genes with a sibling

Of the loci where humanity have different alleles two whole siblings have identical alleles. This is a theoretical number for average siblings in a population with no inbreeding or any population structure, actual siblings tend to be much more similar.