Puberty doesn’t happen at the same time for everyone. Most people start sometime between 8 and 16 and are done puberty by around age 21. The average age for kids with ovaries is a bit earlier than for kids with testicles, but that’s not true for everyone. Some doctors think those with ovaries start earlier than those with testicles because they can reproduce for a shorter time. It’s a process that can take several years. Some people start earlier and others later. It may be fast for some, and slower for others.