The Adoptee, Foster Child and step child are 100% more likely
to be killed by non biological parent than biological children.
United States indeed incur greatly elevated risk of child maltreatment of various sorts, especially lethal beatings". Studies have found that not biologically related parents are up to a hundred times more likely to kill a child than biological parents.[5
Powerful evidence in support of the Cinderella effect comes from the finding that when abusive parents have both step and genetic children, they generally spare their genetic children. In such families, stepchildren were exclusively targeted 9 out of 10 times in one study and in 19 of 22 in another. In addition to displaying higher rates of negative behaviors (e.g., abuse) toward stepchildren, stepparents display fewer positive behaviors toward stepchildren than do the genetic parents. For example, on average, stepparents invest less in education, play with stepchildren less, take stepchildren to the doctor less, etc. This discrimination against stepchildren is unusual compared to abuse statistics involving the overall population given "the following additional facts: (1) when child abuse is detected, it is often found that all the children in the home have been victimized; and (2) stepchildren are almost always the eldest children in the home, whereas the general (…) tendency in families of uniform parentage is for the youngest to be most frequent victims."