I think people who are speculating there was a love angle between Queen Mother and Prince Ian got it wrong.
The two of them went to the same school and she met Yian before the crown prince. She had (and kinda still has) an unrequited crush on him. Which is why she cannot let him become king, as then her decision to choose her status (to marry the lacking crown prince and become queen) over her personal feelings pointless. It says so in her character description that was released.
Wait, ML's dad died 13 years ago. ML's brother was crown prince when he got married. That means ML's brother's…
Yes, which is why I believe she faked a pregnancy to get the crown prince to marry her. Without it he would probably have given the throne to Yian and became a carefree playboy (like he was described in his character description)
Did they say she was pregnant for the marriage to proceed ? I don’t recall that. I mean getting married to the…
Yi-an heavily implied someone already had a premarital pregnancy in the royal family (but he would never throw such a tantrum) when he was talking to the Queen Dowager at the beginning of episode 3. Her face suggests he meant her. And it seems the brother would not have gone through with the wedding without a strong incentive...
Also, about the Queen behavior towards Yi-An. You only need to read her character synopsis that rsooinna posted:
"After entering the royal school instead of sungkyunkwan, she actually met her future brother in law grand prince lee ahn before her fiance the crown prince. perhaps because of the thought that they would become family, her eyes often went to him. actually he was the kind of man who would catch your eye even if he just stood still. an indifferent expression, a quiet nature, and the desires hidden underneath it all. somehow it seemed like he was similar to herself too.
Maybe that is why. every now and then she would dare to imagine what it would be like if he was the crown prince. if he was not a grand prince but the crown prince, if he was not her brother in law but her husband, how would it have been.
Whenever her heart grew desperate, yirang reminded herself of a queen's life. her destiny to become the king's woman, become an idol to all women, and become a part of history. "
I think I figured out the reason behing Yian's dig about getting pregnant before marriage. In episode 4 we find out that his father died 13 years ago, but Yi-An's brother was still the Crown prince when he got married. And the current king is 8 years old. She lied about being pregnant so that he would marry her.
It says so in her character description that was released.
https://kisskh.at/781538-wife-of-a-21st-century-prince/discussions/150340-character-descriptions-extra-info
"After entering the royal school instead of sungkyunkwan, she actually met her future brother in law grand prince lee ahn before her fiance the crown prince. perhaps because of the thought that they would become family, her eyes often went to him. actually he was the kind of man who would catch your eye even if he just stood still. an indifferent expression, a quiet nature, and the desires hidden underneath it all. somehow it seemed like he was similar to herself too.
Maybe that is why. every now and then she would dare to imagine what it would be like if he was the crown prince. if he was not a grand prince but the crown prince, if he was not her brother in law but her husband, how would it have been.
Whenever her heart grew desperate, yirang reminded herself of a queen's life. her destiny to become the king's woman, become an idol to all women, and become a part of history. "
It's unrequited love/crush on her part.
In episode 4 we find out that his father died 13 years ago, but Yi-An's brother was still the Crown prince when he got married. And the current king is 8 years old. She lied about being pregnant so that he would marry her.