In Italian, I would say ho la tua età (litterally, "I have your age") Since in English it is "I am twice your age," I guess it is one of those cases where Italian uses avere ("to have") while English uses to be.
Is "I am your age" correct/acceptable, in English?
I'm your age is a perfectly normal construct in English, as would be similar constructs, such as:
Here are a few sample conversations where you might hear these. The first is a conversation between Fred, Ed, and Ed's wife Karla (who all happen to be 32):
Ed: How old are you, Fred?
Fred: I'm 32.
Karla: Oh! You're our age!
Here's a conversation between two mothers:
How old are your twins?
They're 6.
Oh, they're the same age as Joey. (or, Oh, they're Joey's age.)
In some cases, the word same – whether it's explicitly stated, or omitted and implied – is often used in an approximate sense, meaning "close to the same age." Imagine a man who is 37, married to a woman who is 38, talking about a new employee at the company:
A new guy started work today.
Oh, how old is he?
I'd say he's our age.
The speaker here is simply saying:
"I would guess he's in his mid- to late thirties – around the same age as us."
In this context, he's our age doesn't mean that the new employee is exactly the same age (which would be impossible anyhow, since the couple are not the same age).
Yes, you can say it, but perhaps "I am the same age as you" is more common.
