  In the present paper we study two qubit entanglement in the most general
$XYZ$ Heisenberg magnetic chain with (non)homogeneous magnetic fields and the
DM anisotropic antisymmetric exchange interaction, arising from the spin-orbit
coupling . The model includes all known results as particular cases, for both
antiferromagnetic and ferromagnetic $XX, XY, XXX, XXZ, XYZ$ chains. The
concurrence of two qubit thermal entanglement and its dependence on anisotropic
parameters, external magnetic field and temperature are studied in details. We
found that in all cases, inclusion of the DM interaction, which is responsible
for weak ferromagnetism in mainly antiferromagnetic crystals and spin
arrangement in low symmetry magnets, creates (when it does not exist) or
strengthens (when it exists) entanglement in $XYZ$ spin chain. This implies
existence of a relation between arrangement of spins and entanglement, in which
the DM coupling plays an essential role. It suggests also that anisotropic
antisymmetric exchange interaction could be an efficient control parameter of
entanglement in the general $XYZ$ case.
