Kinsmanship definitely plays a huge role. What is even important, however, is co-religionism. Turkey's present government can be considered a sponsor of terrorism, as has been proven by the active role it played in fake passports scheme that involved Turkish officials in their embassy in China.
Now the outflow of extreme religious fanatics and terrorists (their number is quite small) from China is a welcome news. Russia, too, seems to be not much bothered by the outflow of terrorists from the Caucasus region into Syria via Turkey.
This may explain why Beijing and Moscow have remained relatively silent as thousands of jihadists flocked to Syria via Turkey. What these governments are more careful about is to make sure that those terrorists are unable to come back.
In fact, a person from China and Russia that went to Turkey and stayed there couple of months will practically have zero chance to come back, except illegal border crossing. This also explains China's increased efforts to strengthen border control and anti-terrorism units.
I myself have conducted a research on Turkey's (in mostly civilian capacity supported behind the scene by the present government) involvement in Xinjiang radicalism and terrorism, relying on factual data. I noticed that Chinese officials are quite aware of what is going on and who are the puppets and who are the puppet masters.
Expect the unexpected. Once they leave China on fake passports, join the holy war in Syria and spent several years there, they are as much Chinese as they are Gandhi.