In-plane magnetic-field photoluminescence spectra from a series of n-type modulation-doped GaAs/Al0.3Ga0.7As coupled double quantum wells show distinctive doublet structures related to the tunnel-split ground sublevel states. The magnetic-field behavior of the upper transition from the antisymmetric state strongly depends on sample mobility. In a lower mobility sample, the transition energy displays an N-type kink with field (namely, a maximum followed by a minimum), whereas higher mobility samples have a linear dependence. The former is attributed to a coupling mechanism due to homogeneous broadening of the electron and hole states. The results are in good agreement with recent theoretical calculations. © 2000 American Institute of Physics.