Twin-to-twin transfusion syndrome (TTTS) no relation killing
In humans
Siblicide can also be seen in humans in the form of twins in the mother's womb. One twin may grow to be an average weight, while the other is underweight. This is a result of one twin taking more nutrients from the mother than the other twin. In cases of identical twins, they may even have twin-to-twin transfusion syndrome (TTTS). This means that the twins share the same placenta and blood and nutrients can then move between twins.  The twins may also be suffering from intrauterine growth restriction (IUGR), meaning that there is not enough room for both of the twins to grow.  All of these factors can limit the growth of one of the twins while promoting the growth of the other.  While one of the twins may not die because of these factors, it is entirely possible that their health will be compromised and lead to complications after their birth.
Siblicide in humans can also manifest itself in the form of murder.  There was a significantly greater proportion of accidental deaths in half-siblings, stepsiblings, and siblings-in-law than in full siblings.  This type of killing (siblicide) is rarer than other types of killings.  Genetic relatedness may be an important moderator of conflict and homicide among family members, including siblings.  Siblings may be less likely to kill a full sibling because that would be a decrease in their own fitness.  The cost of killing a sibling is much higher than the fitness costs associated with the death of a sibling-in-law because the killer wouldn't be losing 50% of their genes.  Siblicide was found to be more common in early to middle adulthood as opposed to adolescence. However, there is still a tendency for the killer to be the younger party when the victim and killer were of the same sex.  The older individual was most likely to be the killer if the incident were to occur at a younger age.
no relation