Double Dulahan
During a MMF threesome, with the F in the middle of two M's, you must insert both your nozzles with confidence, thrusting deeply and truly in order to touch the tip of your bro on the other end. Once you've done the double dulahan, your bond can only grow stronger.
I've seen the way you look at me bro, you want to take our friendship to the next level? Call up Becky, she'd be down to facilitate a double dulahan.