How does James Bridge the bridge?

James had a bridge and it was dark when crossing the bridge, so there must be lights. It takes 1 second for James to bridge the bridge, 3 seconds for James's younger brother, 6 seconds for James's father, 8 seconds for James's mother, and 12 seconds for James's grandfather. Each time a bridge can be crossed by a maximum of two people, the speed of the bridge depends on the shortest speed of the bridge, and the light will go off 30 seconds after it is ignited. Q: How does the James family bridge the bridge?

I believe that everyone has read this question. So let's talk about how the James family has passed?