You can become a model - if you have a great overall package. Few things are from birth but generally you must decide from you teens whether you wanted to be a model or not.
Here are few things which you must have
* Good height (minimum 5 feet 10 inches , 6 feet 1 inch is ideal) (height range between 5 feet 11 inches to 6 feet 2 inches is preferred)
* Good physique [good chest (40-45 inches)], waist (32 avg)) (weight 140-165 lbs) Muscles are not always required.
* Good hairs (sometime bald headed people do look good)
* Body structure (broader body structure - chances are bright for becoming a model)
* Face structure (manly face preferred)
* Facial or body hairs (its always better to have them - not always nessary)
* Lastly communication skills do matter (as a way to impress people or to get a break)
* Be in news (currently the latest trend - if you get a small role or something -- try to do some silly or funny thing to catch the attention of media)
Remember the above stats is not for a body builder. You have to decide whether to become a model or a body builder.
Tip : The best way to find out whether you can become a model or not is to have a look at top 1000 models and see whether you are similar to someone or not