This ending kind of sucked. Didn't address her misunderstanding of the cheating, didn't address that they'd still have to lie to everyone, didn't address him "not making her happy". It was kind of just drama for dramas sake and then a "and everything was okay."
how so ?
I think you missed the root of all the problem, or the whole point of the drama.
-The cheating is easy to clear up. is just a trigger event, not at all the main point of the conflict, so it could just tell off-screen. Never the point to focus on
-Have to lie to anyone. yeah. Not the main point, Also what else do you propose ? that just grounded and realistic. i dont think it ever show this is any thing that matter except for the go back and "make it right". which just mean live with your own right, doesn't follow just because social think incest is disgust. so just keep in house secret for now. don't need to change the whole world. that not something someone can did in one lifetime.
-didn't address him "not making her happy". It did, By address the root of the problem. that changed now. so you indeed missing the point, i guess
So what is the root of it all ? that is they both while mutual love each other, don't know how each other feel and so they don't know what to make out of their relationship and commit themself fully to go with this "newly married". They lie to others they are couple. But both just follow the flow, behind close door they still act like brother and sister and never really talk this out. So this whole "lie" is their own lie, actually. They both want it but at the same time just keep up the act on a whim on this "JUST TEMPORARY" lie, that can go back to brother and sister as you can see in the very final arc just now.
But now they done the baby making, tell they love each other. They did the marriage again now but actually fully commit to it. So yes, the ending do solved all the drama