Questions about cat season and pregnancy

Question
Can a younger female cat (app 6 mos) get impregnanted by her older housemate (app 9 mos) before she goes into season for the first time?  He has an appointment in 8 days and I am concerned that maybe I should separate them until then.  She is next.

Answer
If its possible to keep them separated for the next week, then it surely cannot hurt to do so - no sense in taking a chance at having an unwanted litter of kittens.  If it isn't possible - or easy - then the best indicator is their behavior.  Both of them are old enough to reproduce now, so if she is becoming more vocal and loving and/or he is becoming more aggressive, following her around or starting to spray, then that probably means she is in heat, and they definitely need to be kept apart.

Amanda