This is from urban dictionary:
"According to BronyStudy, the age of bronies ranges from 14 to 57, with the average age being 21 years old. The fandom is predominantly male, with approximately 86% of bronies being male."
More interesting brony stats:
"According to BronyStudy, approximately 84% of bronies described themselves as heterosexual, 1.7% described themselves as homosexual, 10.3% described themselves as bisexual and 3.8% as asexual. This is about an average distribution of sexual orientation."