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.
The genetic information from the other parent is different. If you are testing to determine if you are a full sibling (sharing both parents) or a half sibling (sharing only one parent) it is helpful, but not necessary for an accurate result, to have the mother of one of the alleged siblings submit a DNA sample.