the pair from dewsbury , west yorkshire , have not been in contact with their families for several days and can not be reached on their mobile phones .
one of the boys is believed to be a relation of hammaad munshi , who was just 15 when he joined a cell of islamic fanatics targeting the royal family .
he was arrested on his way home from a chemistry exam in 2006 and found with two bags of ball-bearings - key material for a suicide vest .
the south dewsbury area has been linked to a number of extremist plots .