Complex sentence: Their first child, Jake, was born on 12 February 2003, and was joined by a second baby Georgina on 11 October 2004, which led to her taking some time off from the band's activities.
Split into simpler sentences: Their first child, Jake, was born on 12 February 2003, and was joined by a second baby, Georgina, on 11 October 2004. This led to Caroline taking some time off from the band's activities.