Same-sex marriage, also known as gay marriage, is marriage between people of the same sex, either as a secular civil ceremony or in a religious setting. 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.
DNA between siblings are similar if you share the same biological parents. The genetic information you gain comes from both of your parents, and are a result of fertilization of 2 haploid cells fusing to form a zygote that has a diploid number of chromosomes.
Identical twins have exactly the same DNA. They will be the same sex and they are more likely to look like each other. Fraternal or non-identical twins develop from two separate fertilized eggs. Non-identical twins will share on average half of their DNA, similar to the percentage of DNA shared by two siblings who are not twins. Fraternal twins can be the same or different genders.