Younger siblings are always more attractive

[AnyWetCuntweaselsInTheFuckerGr]

.. and frequently cleverer, funnier and generally more talented.

I am struggling to think of a counter-example from my personal experience.

I'm the youngest and by far the better looking .... My DH is the youngest and he has two very very ugly sisters.

The Bro's question .... Luke the actor is the eldest and Matt the singer is the youngest !!!

I conclude your theory is correct !!!

Well done !