Is there a minimum age limit on pillions?

Re-registered (was on old site as Smarty) but unfortunately only to put my bike up for sale. Just don't use it and it's a shame for it to be sitting in the garage doing nothing.
On the plus side, selling it will enable me to buy a new 2014 Gas Gas trials bike to replace my current 2004 model.
So it's hello from me and goodbye from him!