depuis qu’il était enfant
I've known him ever since he was a child.
Je le connais depuis qu’il est enfant.
Tom has lived in New York since he was a child.
Tom vit à New York depuis son enfance.
I've known Chris Reilly since he was a child.
Je connais Chris Reilly depuis qu’il est enfant.
— The Wind That Shakes the Barley (2006)
Tom has known Mary since he was a child.
Tom connaît Mary depuis qu’il est enfant.