William Wilde is the grandfather of Jordan C. Wilde. He has a brief appearance during the prologue of the series, and Jordan wears a dogtag with his name on it at all times.
In 2050, William was the leader of a group of space explorers that made first contact with intelligent alien life. This discovery paved the way the Humans to do business with the aliens and gave an extra boost to their already rapid expansion into space.
However, the Crogs did not approve of the Humans' rising power. In the colonies, a a series of skirmishes broke out from 2055 to 2056. During this time, William was taken prisoner while exploring the Crog area. This is most likely the event that is shown in the prologue when he steps out of his ship and is quickly surrounded by heavily armed Crogs.
It is rumored that William revealed top secret information to the Crogs regarding Earth's defense system. Whether this is true or not has never been confirmed, but it is probably the reason why Jordan has such an intense hatred for the Crogs. It is also unknown if William survived his imprisonment, but chances are that he did not.