At what age is it inappropriate that my daughter has two boyfriends? She says my opinion is invalid because I cheated on her dad whereas she's honest with both guys, but I think she's side-stepping the point.

Actually ... Your daughter is correct.

As long as everybody is aware, it's not "cheating".

In fact, it used to be quite common that females would have multiple "suitors" at the same time.  After all, the point of dating is to determine the type of person you want to spend your life with.  And if you limit yourself to 1 person at a time, it will take a LOT longer to discover "the one".

Well, having a boyfriend when you are already married is in no way similar to being single and having two (or more) boyfriends.

And given the time it may take to find the man you are going to marry makes "sequential" rather than "concurrent" relationships impractical.

Why not be the successful suitor by standing out from the crowd?

I think you are concerned about some of the practicalities you encountered in your previous situation---but there is no need for your daughter to involve herself in the type of secrecy was probably necessary for you to maintain.

Affairs are usually psychologically understandable, but frequently are intellectually incomprehensible to outsiders.  You need to maintain credibility with your daughter for future purposes.  I would suggest you find a way to admit that you were probably wrong in your present evaluation of current status with the two boys, so that she no longer automatically discounts your opinions on such matters. You still have advice about relationships that she can use in the future.

Perhaps your daughter has become the teacher . . And you the pupil.

Honest and open communication is healthy . . If she is able to achieve this and all three participants are being treated fairly . . And no one is getting hurt . . What harm is it?

You should make more efforts to communicate your feelings with your daughter . . . Make sure to tread lightly since hypocrisy is not an attractive look.

If she's not in a committed relationship with either of them, it's her choice if she wants to date more than one guy at a time.  She's even being honest with both of them and they're obviously OK with it.  I think you should stay out of it.  You cheated on your husband which is an entirely different thing.