How old was Jane Seymour when she died in childbirth?

It is unclear when Jane Seymour was born. But most historians believe it was around 1507-1509. Which would of made her at the time of her death on 24th October 1537, either 30, 29 or 28. Most people think 1508 for her birthdate, but that would make her born the same year as her brother, which seems unlikely. 1507 as well seems unlikely for her brother's were older than her. So i believe she was born in 1509 and she died at the young age of 28.