Equanimity is the mind that wishes liberation and enlightenment for friend and foe alike, but we might sometimes think this only requires that we not discriminate against our enemies. That is indeed so: we should not wish our enemies any lesser good than we wish our friends. But that is not the full meaning of equanimity.
Equanimity also entails that we do not assign greater importance to the joys and sufferings of our dear ones. Our friends’ joy and suffering are no more (nor less) significant than the suffering of our enemies, or of those whom we do not know personally.
We do have the duty to perform physical and verbal acts of compassion and kindness toward those who are closer to us, but we should not grant them a privileged status over other beings in our heart and mind. This duty is merely an effect of the condition of proximity, not the result of a special and unique motivation to favor those whom we like.
The Dharma does not advise us to be cold and indifferent toward the suffering of any sentient being —on the contrary; we should consider every being as our only child. But the Dharma does call us to equanimity: each and every ‘only child’ must be as dear as all others, without partiality. This is the vision of the Buddhas.