See Article: Relationship with Gwen Tennyson
In the original series, Ben's relationship with Max seems to be that of a father and son, because the majority of the series took place in the summer and Max was the only guardian available. When he was seriously injured in The Alliance, Ben went full strength with Four Arms and brutally destroyed Vilgax's robot drones as they were the catalyst for his injury. His relationship with his grandfather has not changed much at all during Alien Force, Ultimate Alien, and Omniverse.
Carl and Sandra Tennyson
Ben has stated that he loves and cares about his mom and dad, and that they're good parents and raised him well enough to become the person he is today.
Ben and Lucy get along quite well in both the original series and Omniverse, though Ben was nervous about dancing with her in Big Fat Alien Wedding. However, this was likely as he was just nervous in general, and during the Omniverse flashbacks, was shown to enjoy her company, which she reciprocates.