This is a variation on leg lifts with a twist to add extra focus on those inner-thighs. Basically you are using one leg to lift the weight of your other leg. Working the inner-thighs of both in the process.
How to do it:
Using a mat find a comfortable spot to lay down on your side. Extend your arm nearest to the floor out straight, as if you were reaching for something.
Hold your legs together and slowly raise them both as far as you can comfortably do so. Keep your toes pointed forwards, and control the movements slowly.
The form you want to keep is your upper body flat to the floor, and pivoting at the hips only. Hold the position for 1-2 seconds when your legs are elevated, then slowly return them to the floor. 1-2 sets of 15 reps per side is ideal.