Also stated in the Abhidharma-kosha-shastra is that some children may suffer the effect of seriously negative karma that their parents accumulated. If children can suffer the consequences of their parents's negative karma, is it not contradictory to the Buddhist teaching that one reaps what one sows and that no one can assume other's karma? The Abhidharma-kosha-shastra explains that these children themselves already have certain negative karma. Due to the close relationship between the parents and their children, the ripening of the children's negative karma may be expedited when the parents commited extremely evil karma. There are many such documented cases both in the East and the West. Generally speaking, it is very difficult to directly prove the existence of causality because our eyes cannot look beyond this life for causes from the past lives and effects in the future lives. Nonetheless, through indirect means, as shown by the example above, it is possible to prove the link between cause and effect. Not only is samsara conditioned by causality, but also nirvana and liberation. Therefor, if it is liberation that we seek, we must plant the seed of liberation, which will then yield the fruit. Such is the view of Buddhism. 

~Depicted from FROM BELIEVERS TO BODHISATTVAS