i think they need tourist visa....

 

I'm not sure. They could if they were *dependent* family members - then the same rules would apply as for a non-EU spouse of an EU citizen. Since this is not the case, I would expect that they might need a tourist visa. The question would then be whether they get this via some expedited/cheaper method than what it would normally be.
Unless someone else knows the answer, it's probably best to call UK visas and ask. And please post here what they said... ;-)
Sebastian