Adoption is now ruled out, and the succession passes, upon death or abdication, to the direct legitimate descent of the previous prince, failing which to his siblings and their descent,
This is no longer the case apparently .
Thus the throne can now pass from Albert II to his sisters and their children. The new law, however, restricts succession to persons holding Monegasque citizenship at the time of the demise of the previous prince.
http://www.heraldica.org/topics/national/monaco.htm#change2002