Books with title X Files YA

When two grisly identical murders happen simultaneously on different coasts,Mulder and Scully have only one clue:two identical girls who may or ,may not be criminally involved.Their investigation leads them to a DNA-splicing doctor and a terrifying question:Were these little girls created as killing machines?Mulder and Scully need to find out,before the next crop of killers is born...

A man's body is discovered in the New Jersey sewer system, and a ‘routine' murder investigation ensues. But when several workers are attacked by a vicious sewer-dwelling monster, it becomes clear that something much more sinister is going on underground. Mulder and Scully soon find themselves on the slimy trail of a creature as disgusting as it is dangerous.