The big question is to what degree it was organized, or whether the older brother's social problems (inability to connect etc.) so alienated him that he just seized on the most empowering role model he could think of, an Islamic rebel. Chechnya is a country that has been ruled pretty poorly by Russia at it's not so long ago that Chechen Muslims were seen as heroic freedom fighters in the west.

In short, it's unclear whether they were actually involved with any organized jihad groups or just developed a personal obsession with the ideas and copied the methods.