You did it! We figured this one out! It is a truth universally acknowledged (by me for certain) that the Bitchery pretty much knows everything, and really, it's true. Scroll down to see the solution for this HaBO - and many thanks!
This HaBO comes from Kim, who wants to find this historical romance:
The book is about a young woman who goes to live with a duke(?) she is supposed to marry. This aristocrat has a twin brother who lives in the mansion (the hero of course). The young woman believes that her “maidenhead” is her actual head and when the twin sees it, she panics and yell at him for “taking her maidenhead.” The duke isn’t really interested in the girl; he is having an affair with the butler. The twin ends up getting the girl pregnant, and the duke wants to sell the baby to the king who has a demented queen who thinks she is pregnant.
I don’t remember much more about the book, other than the title had “Star” in it somewhere and it was probably written in the 80s.
Wow that description really took a turn.