Why should your Boss have to know about your PREVIOUS relationship with your co-worker?
2) Your Boss... has, on his own, has decided to use your "Ex" as his point person. For whatever reason... your Boss perhaps connects with or likes this person as the point person of the team. So therefore that is what your Boss has done.
I am sure, others, just like you, might feel the same way and also want to jockey for a better position and get credit for it etc.
But, this is also your Bosses problem and creation.
And now your Ex, sure... he feels more respected by the Boss... because the Boss is treating him as his point person.
If you want to question the Boss as to WHY your Ex is his point-person and not you... well, the Boss might get a little confused, because it probably is not being done on purpose... but you would like to tell the Boss that he is 'wrong?"
And, no matter what, it has NOT been formerly designated, that your Ex is a "Supervisor," right?
If anything, just ask your Boss "How did you like my idea for Project A, in which I said...." and tell the Boss. Y.o.u.r.S.e.l.f
You don't have to let only your Ex, tell your Boss things. Right?
Or send your Boss an e-mail. This would also then create documentation of it and your ideas.
DOCUMENT all of "your" accomplishments and ideas.
But with ideas, anyone can claim them.
Or, talk to your Ex about it.
Or don't tell your Ex, any ideas anymore. Since the "Boss" is indirectly giving him credit, for it. If your Boss is indirectly giving your Ex credit for it... it is not your Ex's fault.
Your Ex is only the carrier pigeon.
If anything, maybe just have a meeting with your Boss??? About your ideas and performance.
And the thing is, maybe people do already know that you and your Ex had a relationship.
Those things are hard to keep secret.
What a tangled web.
Your Boss, makes his/her own decisions.
Not your Ex.