Delayed Puberty

Even though, according to your age and ancestry, you would typically have physically developed adult characteristics, these characteristics are delayed or absent in you. Whatever the typical age of maturity for your ancestry, it takes you twenty percent × IE longer to develop these characteristics. Until you reach this age, you have advantage on Charisma (Deception) checks to present yourself as a child and disadvantage on Charisma (Intimidation) checks.

Real-world Examples

Constitutional Growth Delay, Celiac Disease, Klinefelter’s Syndrome, Turner Syndrome

Assistive Options

Because this can lead to being infantilized due to being perceived as a child, support and respect from your party helps reinforce to others that they should respect you and treat you as an adult.

Magical Assistance

Magic that affects a person’s appearance and voice, such as a Seeming spell, can assist with this for the duration.