Maternal love and filial

Is maternal love a virtue or an instinctive feeling common to humans and animals?
"The one and the other. Nature has given the mother love for her children with a view to their preservation. In the animal, however, this love is limited to material needs; it ceases when care becomes unnecessary. In man, on the other hand, it lasts all his life and involves a dedication and self-sacrifice which are virtues. It even survives death and follows the child beyond the grave. You can see, then, that there is something more in him than in the animal".
Given that maternal love is in nature, why do some mothers abhor their children, often from birth?
"Sometimes it is a trial chosen by the spirit of the son, or an atonement in case he has been, in his turn, a bad father or a bad mother, or a bad son in another existence. In all cases, the bad mother can only be animated by an evil spirit who tries to hinder the son's spirit, so that the son succumbs to his chosen trial. Yet such a violation of the laws of nature will not go unpunished, while the spirit of the child will be rewarded for the obstacles it has overcome".
When parents have children who cause them grief, are they excusable for not having lavished on them the tenderness they would otherwise have had for them?
"No, because it is a burden that has been entrusted to them, and their mission is to do their utmost to bring them back to good. However, these sorrows are often the consequence of a bad habit that they have been allowed to get from the cradle. In that case, they reap what they have sown".