We consider a system of two heavy quarks in a cloud created by a light quark within effective string models which purport to mimic QCD with two light flavors. The results point out the universality of the string tension, the quark-diquark symmetry at small separations of the heavy quarks, and the symmetry of the ground state. We also make an estimate of the string breaking distance and a few comments of a heavy-light diquark [Qq].