Can't be longer then "Charlotte Bernadette-Anne".... middle names from her Grandmothers on each side.
Didn't think how the poor bugger would go writing out official documents.....
My sister is Brhianan Frances Victoria - so long that on her testamur from uni they could only fit the first two names, even though she put them all on the paperwork for graduation!

My younger brother also has three names, but my older brother and I just have two. So even in the same family you don't have to keep the same number of names.

I have picked three for a girl, but two if our first is a boy, so just go with what you like, Smithy!