Kids for sale!!

How is it that no matter what both of the kids want the same toy?????
I find another toy just like it and they still want the same toy?????
all it seems my children having been doing today is see who can make who scream the loudest!!!!
I am about to go insane!!!!!!
I mean one has the screaming down to an art form she knows how and when to scream to get attention!!!
The other thinks that it is funny to make her sister scream and the louder the funnier it is!!!!
Please let this help me not go insane too quickly!!