  We re-examine the results of A. Thilagam [Phys. Rev. B 55, 7804 (1997)], who
calculated the ratio of the binding energies of the two dimensional exciton
complexes. We point out that, for charged biexciton complexes, this calculation
is oversimplified, and these systems do not always form bound states if they
interact via pure Coulomb interaction. If experiment proved the existence of
these objects, their bindings would have to be explained by other mechanisms.
