Son âge est secret.
(une) langue secrète
un secret
To say "her age" in French, you would say "son âge".
ton/votre petit secret
Secret love could be translated as "amour caché" or "amour secret".
secret, secrète
son age
You can say "Avoir un âge similaire" in French to express "Have similar age."
the Stone Age is called " l'âge de Pierre " in French.
Two words for you... 'yahoo translator'
un petit secret
Aucun âge