Hello, Mr. Cornwell

I’m currently reading The Burning Land and I have been a little confused with the stories timeline. For example, at the first chapters of the book, it is said that Gisela and Uthred’s youngest son, Osbert, is 2 years old. However, a few pages later, Uthred says that he hadn’t see Aethelflaed for four years. Assuming that the last time he saw her was at her rescue at the end of Sword Song, and that at that time Gisela was pregnant with her third child, and noting that Gisela said that all her three previous pregnancy were successful, how does her and Uthred’s third child, Osbert, is only 2 years old? If she only had three children before, shouldn’t Osbert be around 4 years old?

I look forward for your enlightenment on this matter.

Rodrigo Diniz