Audio keyframes seperate

The red line is the Right Channel, and the green one is the Left. Unfortunately, when using the graph editor, you can't grab both handles at the same time, so you have to match the position of the Bezier handle visually. It's the same as grabbing one position or scale property when you try to edit the values on the Graph Editor. 

A common way to ease in or out of a fade would be to use the Keyframe Assistant.

If you really need to finesse an audio edit in After Effects, the best, and by far the fastest solution, would be to select all of the audio layers and choose the Edit/Edit in the Audition menu. If you are working on more than one shot in a comp (Comps are usually only one shot, one thought, or, at most, one short sequence) and trying to edit a movie, the most efficient workflow is to render your AE comps and do the final editing in Premiere Pro, including adding sound effects and doing the final mix. If the mix requires more finessing than you can get in Premiere Pro, you can also edit a Premiere sequence in Adobe Audition. I don't know any pro that would spend much time fine-tuning an audio fade using the graph editor.

The only way I know of matching the curve would be to add an expression control slider to the layer, tie the left and right channels to the slider, and then edit the curve on the slider control.