The War of the Twins is an event which takes place between the events of Quest for Lost Heroes and Winter Warriors. According to the Drenai Timeline it takes place in the year 1433.
Little information is available about the war in itself, but it is a war between the conquered Drenai and the Nadir, and the twins are the sons of Jungir Khan; Tsubir Khan who is the child Asta Khan - the shaman in Quest for Lost Heroes - raises to lead the Nadir empire, the other child - the one Asta has no idea even exists - is named Aradan and is raised by Ravenna and Chareos as a double-heir to Dros Delnoch and everything connected to the Earl of Bronze.
What little is known is that the Nadir eradicate the Sathuli, The Thirty (the temple during the time period) is destroyed to the last man and no temples are mentioned beyond this point and yet still the Drenai appear to have won as in Winter Warriors the Drenai have reformed as a kingdom and have conquered other nations.
This is a Family tree created by myself, pulling together various bits of information from the books, the Drenai Timeline and the Wiki here. Any mistakes are my own and I am aware there are gaps in the information presented.