The “fruit tree” for Stephen was not his biological heritage; but it was something that proved to be even stronger. There was an indwelling of spirit between himself and Jesus that led him to publicaly proclaim Jesus as Lord, and to very boldly accuse the Jewish leaders of their sin in not recognizing who Jesus was.
When Stephen had incited the crowd to the point that they pulled him into the street and started to stone him, he said, “Lord, receive my spirit,” and “Lord, do not hold this sin against them.” Do those words sound familiar? They are the same words that Jesus spoke from the cross. The fruit did not fall far from the tree.