Added to this, if the death were for some reason other than natural, young brash adventurers might take it upon themselves to avenge the wrongful death of their friend. Death can be a strong motivator in aligning characters for the common cause of revenge. This can be a tough one to work with, but it can be done. In feudal societies, the common setting for many fantasy RPGs, war and conflict were a common occurrence. In times of need, many were willing to pick up sword or staff to defend their homeland - from all across the kingdom.
Adventurers are all the more likely to travel forth in search of the glory of battle.
The problem with this scenario is that the characters are likely to become stuck in a war and unable to set off on adventure without certain risks. Characters that choose to leave an army in search of adventure would likely be seen as deserters. Although this might be a campaign twist that can add more flavor to your sessions, I recommend that the GM have the adventurers converging on a small battle or border skirmish that ends before the characters become involved. One way of creating an interesting scenario for adventurers to meet is to develop your own specific event. My personal favorite is to create an 'adventurers festival,' mush like the medieval tournaments.