The idea is that the cord blood could help close relatives as well- brother or sister of kid - incase of genetic disease. The blood bank will screen the blood and us for genetic disease . What you mentioned is somewhat right in that if the kid has a problem (genetic disease) very early in life, then the cord blood may not be of help .But it's later that really matters more . . . The thing is though, that it is very likelyk that there will be more and more uses for cord blood - things that we don't know as of yet -