Well, actually, about that.
According to DSM-5, which is basically the thing for diagnostic criteria in the US:

Pedophilic disorder

302.2 (F65.4)

• A. Over a period of at least 6 months, recurrent, intense sexually arousing fantasies, sexual urges, or behaviors involving sexual activity with a prepubescent child or children (generally age 13 years or younger).
• B. The individual has acted on these sexual urges, or the sexual urges or fantasies cause marked distress or interpersonal difficulty.
• C. The individual is at least age 16 years and at least 5 years older than the child or children in Criterion A.

Note: Do not include an individual in late adolescence involved in an ongoing sexual relationship with a 12- or 13-year-old.

Specify whether:

• Exclusive type (attracted only to children)
• Nonexclusive type

Specify if:

• Sexually attracted to males
• Sexually attracted to females
• Sexually attracted to both

Specify if:

• Limited to incest

So it does generally include 13.

Edit: Improved formatting (trying to copy the book).