Pete Postlethwaite was 46 in Alien³ when he played the character 'David'.
That was over 32 years ago in 1992.
In 2011 he died aged 65, starring in 79 films in his career, 57 of those after Alien³ was first released. If he were alive today he would be 79.
In Alien³, I think Pete Postlethwaite looks: