in his/her youth
Est-ce que ta mère jouait du piano dans sa jeunesse ?
Did your mother play the piano in her youth?
Il a honte d'avoir été fainéant dans sa jeunesse.
He is ashamed of having been lazy in his youth.
Il avait beaucoup voyagé dans sa jeunesse.
He had travelled extensively in his youth.
Il en a eu pas mal dans sa jeunesse.
He had quite a few in his youth.
Marie était une petite maligne dans sa jeunesse.
Marie was a little smart girl in her youth.
Marie était coquine dans sa jeunesse.
Mary was naughty in her youth.
Tom était espiègle dans sa jeunesse.
Tom was mischievous in his youth.
Dans sa jeunesse, il était connu pour être un bon pianiste.
In his youth he was known to be a good pianist.
Il a pris l'habitude de fumer dans sa jeunesse.
He got into the habit of smoking in his youth.