The Perfection of Loving-kindness - Attachment or loving-kindness

If we only consider the outward appearance of our deeds, attachment and loving- kindness seem to be similar. When we perform a good deed for the sake of someone who is close to us, whom we respect and love, it seems that this is motivated by kusala, by metta. However, why can we not be kind in the same way to someone else, no matter who he is? If there is true metta it should be exactly the same whether we perform an act of kindness to someone who is close to us, with whom we are familiar, or to a person we are not familiar with. If there is true metta, if we want to develop the perfection of metta, we should not restrict metta to particular persons. When we limit metta, we should investigate the characteristic of the citta at that moment, we should know whether it is kusala citta or akusala citta.
We read in the Tipitaka that performing deeds with metta is like the conduct of a mother towards her child. If we look at the outward appearance of deeds we may wonder whether a mother has true metta or whether she has just selfish affection for her child. She has to sacrifice everything for her child when she takes care of him. Sometimes the child is dirty and disagreeable to touch, but she still takes care of him. We should consider whether a mother has true metta for her child, or whether she has only selfish affection. A mother should know her own cittas, she should be truthful with regard to reality: kusala is kusala and akusala is akusala.
It is right that the Tipitaka explains about metta as being the same as a mother’s conduct towards her child. However, we should remember that a mother’s attachment to her child is not metta. If one can have the same conduct towards other people as a mother’s selfless loving care for her child, then we practise metta.
When we see someone else who is kind to a stranger, to someone who is not close to him, we should not wonder why he acts thus, because true metta is not restricted to particular people. All people are equal, no matter whether they are close to us or not, no matter whether we know them or not.
Did we in our daily life assist others with generosity? If we wish for their wellbeing and happiness, we have loving-kindness towards them. When someone experiences sorrow, when he suffers, we may have compassion and wish that he will be free from suffering. When we wish to help a person who is sick and who suffers pains, when we want to take care of him, we have compassion: we wish that person to be free from suffering.