Cliff's Links
Craig is a valuable friend and brother to have; at least, for Cliff he is. Cliff can't actually speak any discernible language other than the one his kind speak, he never had the capacity to learn to speak the common tongue of this solar system. Cliff is the scientific one, and Craig is the one who does the talking.
Craig loves to work with his brother. Cliff knows so much about what is, and Craig finds it simply astonishing. Craig took it upon himself to learn as many languages as possible so he could help his beloved brother in spreading his knowledge. Craig also has human-like hands, so he can do more with his "default" body than Cliff can, and he uses that to make a set of fake hands for Cliff so he can conduct his own experiments.