well, the other half-vamp-half-human Nahuel reached maturity after seven years. And they describe him as looking around Bella's age or a little younger. So I suppose Jacob and Renesmee will look close to the same age. Well, except for the fact that Jacob is unnaturally tall....lol

Hope I answered your question! :)

I read somewhere that she will look around 17 or 18..but in the book doesn't jacob look like he's around 25??