  The strongest upper bounds on the axion mass come from astrophysical
observations like the neutrino burst duration of SN1987A, which depends on the
axion couplings to nucleons, or the white-dwarf cooling rates and red-giant
evolution, which involve the axion-electron coupling. It has been recently
argued that in variants of DFSZ models with generation-dependent Peccei-Quinn
charges an approximate axion-nucleon decoupling can occur, strongly relaxing
the SN1987A bound. However, as in standard DFSZ models, the axion remains in
general coupled to electrons, unless an ad hoc cancellation is engineered. Here
we show that axion-electron decoupling can be implemented without extra tunings
in DFSZ-like models with three Higgs doublets. Remarkably, the numerical value
of the quark mass ratio $m_u/m_d\sim 1/2$ is crucial to open up this
possibility.
