This is only superficially a prisoner’s dilemma. In a true one, you cannot get a better result for yourself no matter what the other person does, but here if you assume the other person pulled the lever, there is no reason to pull the lever yourself.
To fix this, you can have 4 relatives on the trolley, and 5 of the opposite faction way back on the middle track. Both do nothing, 1 relative of each is killed. One guy switches the lever, their relatives are all fine, other guy loses 5. Both switch, crash with all 8 relatives on the trolley dead.
This is only superficially a prisoner’s dilemma. In a true one, you cannot get a better result for yourself no matter what the other person does, but here if you assume the other person pulled the lever, there is no reason to pull the lever yourself.
To fix this, you can have 4 relatives on the trolley, and 5 of the opposite faction way back on the middle track. Both do nothing, 1 relative of each is killed. One guy switches the lever, their relatives are all fine, other guy loses 5. Both switch, crash with all 8 relatives on the trolley dead.