  In this work we propose a method for including strong isospin breaking in
twisted mass lattice calculations, while preserving flavor identification. We
utilize a partially quenched construction in which the sea quarks are given by
the standard twisted mass lattice action while the valence quarks have an
additional strong isospin breaking mass term. This construction allows for a
practical use with existing twisted-mass gauge ensembles. Additionally, we
construct the relevant partially quenched twisted mass chiral perturbation
theory for both mesons and baryons to O(m_q^2, m_q a, a^2). We provide explicit
expressions for the pion, nucleon and delta masses, as well as the
corresponding mass splittings, and discuss the resulting errors from including
the strong isospin breaking in the valence sector only. Finally, we demonstrate
how the application of this idea can be used, with mild approximations, to
determine the values of both the up and down quark masses.
