KITTY!!! GROSS!!! We will never speak of those things at GA again!
Hey Kevin, regarding your problem at hand. I usually butt in situations like this (shocking, I know).
If Josh is truly gay/bi/questioning, then you are right, they shouldn't be engaged. Unfortunately, he may be trying to 'pass' or bury his guy feelings deeper in the closet with the hope that Kim will turn him fully 100% grade A hetero.
If you want to save them BOTH a lot of heartache, here's what I would do...
Go try to hang out with Josh ALONE. Go do something that two buddies would do. Talk to him more, be his friend. If he is gay, he may just need gay friends who can show him that there is an alternative to a hetero life.
I'm not saying out yourself to him, but be his friend. If you get to know him more, you might be able to better find out what his tendencies are.
If he is gay or has gay tendencies you'd be helping them both out in the long run!
Take Care®,
Vic