Jeff, not knowing what to do in there, decides to see the difference of comfort between Diana's vagina and Megan's vagina. He admits to enjoying it when stuck in Diana's, and hopes Megan's is at least similar... (Alright, let's see how she feels.)
Climbing the front of the diaper, Jeff grabs onto Megan's lips, which are nowhere near as puffy as Diana's. (Bad start, but there's still a shot). Continuing on, he carefully maneuvers himself from standing on the diaper to standing on her lips, which Jeff guesses is sending pleasure to Megan.
Slowly, he spreads open her lips, giving him a view inside of it. (Looks promising inside, although I didn't get to see inside Diana's...). Carefully, he lowers his body down, using the top of her lips as support until he lands just inside of her vagina. This causes a slight stir from Megan, although she sleeps through it. (I probably wouldn't hear the end of it if Megan caught me here... Diana at least is too innocent to do anything, but I don't know about Megan...)
After this, he slowly steps in; Every step causes a twitch, but still not waking her. Jeff steps in as far as he can without moving his head. He then positions his head out past the lips' range, before letting go of the top. With the smaller size, he can lay down between them and still close them on himself. Jeff then takes in the soft cushion of his sister's pussy lips...