Correct me if I'm wrong but deosn't Madelis say during WLL that new Xen was formed a few months before Kenneth joined? Also considering how people in the past know about Miera, the way the stormchasers recruit people and how old Irvin seems to be it deosn't seem implausible to think that Irvin's daughter died in Miera before he evacuated and/or was recruited. Maybe they used his daughter's death as his motive to get him to join?