Unique bicycle built for two

[Grandpaw]

Went over to my cousins house and he and his wife are in to bike riding. He also likes to go with his dad that is in his seventies but his dad gets tired while riding so he fixed these two bikes where either one or both can pedal and either one can steer. I thought it was a little different so I thought I would post a picture of it. By the way you can't tip it over, Jeff