Responses
In the novel Yongshan indeed rapes Yongqi; the manhua doesn't explicitly shows it, but it's still heavily implied.
The book is under the incest tag so that should answer your question.
I binged read this from chapter 1 and I'm sooooo soo confused. At first, I thought yongqi was raped by yongshan, but as the story progressesd, it didnt seem so. At this rate, all I see is bromance/brotherhood. I was weirded out by the fact that they are brothers, but since they are handsome....well ٩(๑❛ᴗ❛๑)۶
My point is, what's the nature of their relationship?