Q:

I said to my brother, “Let us go to some hill station for a change.” 

• 1
  I suggested to my brother that let us go to some hill station for a change.
• 2
  I suggested to my brother that let them go to some hill station for a change.
• 3
  I suggested to my brother that they should go to some hill station for a change.
• 4
  I suggested to my brother that we should go to some hill station for a change.