One thing I don't understand about this movie.

I think in that scene Emilie is either flashing back or fantasizing about having sex with a young Antoine.

The young man clearly resembles Antoine....look at his nose and the dark hair and skin. In between encounters with the young man, Emilie remembers a moment with her parents (even though she is still physically represented in the present during this memory) when they ask her about having a baby brother.

Unless it is a memory or a fantasy (maybe Antoine isn't the only one w/ incestuous feelings) it just seems so strangely out of place.

It makes sense to me that it is a memory because just after that scene she moves back in w/ Bruno and hits Antoine when he tries to take her pulse (tells him not to touch her, etc.) and she clearly winces when he tries to touch her.

Maybe she repressed the memory, maybe she was in denia, I don't know.

I have tried to find the answer to this by researching online. All I found was a reviewer who said that scene's purpose was to reawaken Emilie's sexuality - which then drives her to return to Bruno because her sexual needs cannot be met by her brother. This is plausibile...but it seems entirely unrealistic to me that Emilie would have sex with a total stranger in a park. It just doesn't fit her character.

Anyone else have thoughts?

I don't see it as incestuous. Emilie is going through a crisis with the imminent demise of her mother, and is extremely upset and lonely. She has sex with the intern simply because it might make her feel better. Remember, earlier she had stated that she wasn't having sex at all, so this was a moment where she decided to act on her impulses. Unconsciously, it may have also been a statement to her brother that his desire to possess her, was inappropriate. Of course, Antoine would have argued that he had no incestuous desires toward his sister whatsoever. To him, being 'childlike', was a good thing!