Jacen Solo was born during 9 ABY on the planet of Coruscant. He was born to Leia Organa Solo and Han Solo, also born five minutes after his twin sister, Jaina. In 10.5 ABY, he became the elder brother of Anakin Solo. The children spent most of their time away from their parents due to the fact their parents were typically busy.
Jacen and Jaina later attended their Uncle Luke Skywalker's Jedi Praxeum on the planet of Yavin IV. It was there they befriended Tenel Ka Djo, Lowbacca, Raynar Thul, and Lusa. They were also reunited with their childhood friend Zekk and faced many dangers throughout their training.
Not too long after being Knighted the Yuuzhan Vong War began. Jacen faced many tragedies throughout this time such as the loss of Chewbacca, Anakin Solo, and many others. He was also captured by Yuuzhan Vong during this time and managed to escape alongside a Fosh named Vergere.
Once the Yuuzhan Vong War had ended he spent five years in exile. While training with the Fallanassi he heard a cry through the Force which began to increase and he eventually ended his training early in search of the call.
It was then The Swarm War began and he became the informal Master of his cousin, Ben Skywalker. Jacen also visited Tenel Ka during this time and the two had a child named Allana together.
Shortly after the end of the Swarm War, the Second Galactic Civil War began and Jacen became Colonel of the Galactic Alliance Guard also accepting the path of the dark side.