The DNA laboratory extracts the genetic profiles of the alleged siblings and creates a siblingship index.
If the siblingship index is less than 1.00, this indicates non-relatedness. If the siblingship index is greater than 1.00, then the two tested individuals are more likely to be biological siblings. The higher the value of the siblingship index, the greater the likelihood that the two individuals are biological siblings.
To analyze the possibility that the siblings share only one common parent versus two common parents (mother and father), a half siblingship index is obtained. The ratio of the half siblingship index versus the full siblingship index will indicate whether the two individuals are more likely to share only one common parent or two common parents (mother and alleged father).
A siblingship DNA test will provide you with an indication of whether you are more likely to be a full sibling, half sibling or not the true biological sibling of the other tested individual.