Marital Turmoil: Back Off, First Love!

I used to enjoy watching melodramatic TV dramas, so I somewhat understand the destructive power that a so-called "white moonlight" can have on a man.
The so-called "white moonlight"—the more unattainable it is, the more one desires it.
Due to societal reasons, the two of them were destined to never be together. The prestigious family couldn't afford the disgrace, even if they weren't related by blood, the family couldn't bear that shame.
"She is just my sister, don't overthink it!" Faced with my questioning, he always left me speechless.
I have been married to him for four years, wholeheartedly wanting to bear his child.
Unfortunately, he never sleeps with me. I can't continue to sink into this any longer. I need to take the initiative.
First love, please step back!