accessing all of a colliders parents children

I have 2 lists that contain colliders

L1 - var collisionArray = new List.();

L2 - msg.otherList

I want to compare each collider in L2 to L1. If L2 is in L1 i want to then get the parent of L2 and check to see if any of L2.parent.chlid's colliders are in L1 then if the are remove them from L1.

The part that im having trouble with is getting the children of L2. i have started with

//save the original sizes

var listItt : int = collisionArray.Count;

var listIttOther : int = msg.otherList.Count;

  //Get i of the first list

  for (var i : int = 0; i != listItt; i++)

  {

      //Get j of the other list

      for (var j : int = 0; j < listIttOther; j++)

      {

          //Some how access msg.otherList[j]'s children

          //if child.collider = collisionArray[i] remove i from collisonArray

}

}