Genetic Relatedness You share copies of your genes in these proportions with your close kin: 1, ie a complete matching set of your genes, with your identical twin. 1/2 your genes with your sibling or parent. 1/4 of your genes with your grandchild, grandparent, niece, nephew, aunt or uncle. 1/8 of your genes with your great grandchild, first cousin, great aunt or great uncle. Your genetic relatedness quickly dwindles with more distant family members and is least with strangers.