Roddy McDowall was 8 in Murder in the Family when he played the character 'Peter Osborne'.
That was over 86 years ago in 1938.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 1998 he died aged 70, starring in 166 films in his career, 165 of those after Murder in the Family was first released. If he were alive today he would be 95.
In Murder in the Family, I think Roddy McDowall looks: