in his/her youth
Él obtuvo el hábito de fumar en su juventud.
He acquired the smoking habit in his youth.
En su juventud se levantaba temprano.
In his youth he used to get up early.
Ella es orgullosa de haber sido bella en su juventud.
She is proud of having been beautiful in her youth.
Dicen que era una actriz en su juventud.
They say she was an actress in her youth.
Él cometió muchos pecados en su juventud.
He committed many sins in his youth.
Mi padre debió ser buen mozo en su juventud.
My father must have been quite handsome in his youth.
Dicen que él era muy pobre en su juventud.
They say he was very poor in his youth.
En su juventud, mi madre era muy bella.
In her youth, my mother was very beautiful.
Desgraciadamente, el poeta murió en su juventud.
Unfortunately, the poet died in his youth.