Hi Bay,

Indeed in French we use 'avoir' for thirst and hunger and also for ages.

e.g.

Ils ont vingt ans, cette année. 

(They are twenty this year.)

Le chat a soif.

(The cat is thirsty)

Nous avons faim, quand est-ce qu'on mange?

( We are hungry when are we eating?)

Hope this helps!

Hi Bay - the easiest way to 'get' this is that 'faim' actually means 'hunger' not 'hungry', so in French we say, in effect, "I have hunger". It's the same for thirst. Hope that helps!