desde que era niño

since I was a child

→ desde
phrase Rare #25,022
since I was a child Used to say something has been true since childhood. The subject changes with context: desde que era niño, desde que era niña, etc.
SP: Vivo en esta ciudad desde que era niño.
EN: I've lived in this city since I was a child.

Es extraño, no me he peleado con nadie desde que era niño.

It's strange; I haven't gotten into a fight with anyone since I was a child.

— Caché (Escondido) (2005)

No había vuelto desde que era niño.

He hadn't been back since he was a child.

— Sympathy for Mr. Vengeance (2002)

Desde que era niño.

Since I was a child.

Tom conoce a Mary desde que era niño.

Tom has known Mary since he was a child.