  We study the effect of symmetry breaking in a quantum phase transition on
pairwise entanglement in spin-1/2 models. We give a set of conditions on
correlation functions a model has to meet in order to keep the pairwise
entanglement unchanged by a parity symmetry breaking. It turns out that all
mean-field solvable models do meet this requirement, whereas the presence of
strong correlations leads to a violation of this condition. This results in an
order-induced enhancement of entanglement, and we report on two examples where
this takes place.
