learn to tie knots. Like, be a total expert. all sorts of cool knots.
Show them. Offer to stop in and tie one of them up for some really crazy stuff. They'll throw you a bone, maybe let you jack off to the 2 of them kissing, for your trouble.
As time passes, you'll be the 'go to' guy when they decide they want some dick. One of them still fancies the cawk, she just won't admit it. YOU, my friend, can become that safe option/outlet that the anti-cawk partner will not see as a threat.