Fence to Fence Post Gap, Fix a Leaning Fence
You could just use the same fasteners they used for the 2x4s to the post. Align a sister 2x4, 2' is enough, to your 2x4s and fasten away. If you don't have a nail gun, I'd use screws for the sistering so it make it easier to align things up. Nice thing is that you just gained 3" of additional land.