Who is older Firestar or Graystripe?

yes. Fireheart and Graystripe fight in Warriors: Fire and Ice because Fireheart takes up for Graystripe when he is asked to go on the patrol to attack Riverclan. but Graystripe is meeting a Riverclan warrior named,Silverstream who he loves very much and doesn't know what to say. so, Fireheart tells the clan that Graystripe has already fallen into water this leaf-bare and he's not about to do it again. so, Fireheart takes Graystripe's place, eager to attack Riverclan, but the thaw has begun so they can't cross into Riverclan territory. when they return Graystripe calls Fireheart in his usaul friendly tone and Fireheart is hoping Graystripe will thank him for taking up for him but instead Graystripe attacks him saying that Fireheart thought he would betray Thunderclan and Fireheart retorts " Though i'm not sure where your loyalties lie right now!" he and Graystripe roll out from behind the nrsery screeching and clawing. Bluestar summons Fireheart to her den and tells him she didn't expect to see him and Graystripe fighting. but at the very end of the book Fireheart and Graystripe rekindle their friendship.