The term ‘siblings’ refers to brothers and sisters; they need not be of the same gender. When siblings share both biological parents, they are full siblings. The laws of genetics are such that each sibling inherits half their DNA from each parent. Between then, siblings will have 50% of their DNA that is common. This percentage varies, and there are very rare cases where they may have almost 0% in common or most of their DNA in common. Identical twins share all their DNA make-up.
Half siblings have around ¼, or 25%, of their genetic material in common. Half siblings can only share one biological parent; if it is the mother they share, they are referred to as uterine siblings and conversely, if they share the same father, they are called agnate siblings. Siblings relationships can be scientifically investigated using DNA relationship tests. There a number of relationship tests which will tell you the relationship between siblings, specifically sibling DNA tests. These tests may tell you whether you share common parents and thus, give a good indication of whether you are half siblings or full siblings.