Is there a big difference between 13 and 14 Year olds?

People develop at different rates.

Of course, no one grows and changes as the exact same rate as someone else.  It also depends on what your perception of what a 13 or 14 year old looks like...that's different for a lot of people.  If this is about you...your fine- you'll get where you need to be whether you think your behind...or ahead.

Of course it is possible for 14 yr olds to look 13.

Do you seriously think that at the stroke of midnight as your 14th birthday started you suddenly looked older?

My wife was 22 when I met her. As she was also very petite she looked young enough to  get asked why she was paying for adult fares on public transport, which applied from age 14.

St. Philomena was only 13 when she died.  She suffered horrifying torture and cruel martyrdom for her rightful refusal to marry the haughty emperor Diocletian.  St. Philomena is the patron saint of infants, children, youth, and the living rosary, among other patronages.  It is good to recite novenas and litanies in her honor, and to recite her chaplet.  St. Philomena is an early Christian virgin and martyr who was born on January 10 and grew up as a princess in Greece, both of her parents being of royal blood.