Same-sex unions are recorded in the history of a number of cultures, but marriage or similarly formalized same-sex unions were rare or nonexistent in other cultures.
Using this measure, siblings are actually 99.95% the same. The 50% refers more to the amount of DNA we get from mom and the amount we get from dad. So we are more similar to our relatives than we are to a mouse. Let's explore in a bit more detail what the 99.95% and the 50% numbers mean.
Best Answer: The chances of two brothers having the same DNA test result are 0.01% - have a look at the rest of the answer if you want to know how i worked this out. This of course is not the case if the brothers are identical. I think therefore it is highly unlikely that the other brother could be the father but it is still possible. Everyones DNA is actually pretty similar infact we have 99% of the same DNA as our closest ape relatives.