Autumn's Concerto (2009)

Based on a family that has been torn apart. Both men are unknowingly fathers, separated cruelly from their children.

Both are great romances with a touch of the dark side. Autumns' Concerto is one of the best romances out there and the highest rated Taiwanese drama. I always rewatch it for a happy fix.

Both series have the notion of having a baby and not knowing it.

In QoT the female are the one having brain tumor also amnesia
Also rich female lead

While in AC the male are the one who have it
Both also dealing about marriage problem
If the rumor are true about the script from 2010
Then it was around 1 year after AC released

Both stories feature a young single mother who live in a small town. But how each story story plays out they differ from each other.

Ayaka, who works at the bridal department at a hotel, has a beauty that everyone recognizes, yet her personality is the worst. Everyone calls her a "wicked woman" after the way she wraps numerous men around her finger. The one who sets his eyes on her is the hotel's new executive Togo, who is the son of a very powerful person of the town. What are the orders that this King-like man requests of her!?

In both dramas, they fall in love with the main character and are forced to break up. After the breakup, the main character finds out that she is pregnant. over time they will meet and everything will turn out well the family will be together.

In both series there are lovers that are separated then are reunited.
There are other similarities that are spoilers for both series.

Both have love triangle and a the male lead has lost memory.

Both have unplanned pregnancies and the couples in both dramas are constantly misunderstanding each other.

Hyun Jae is only 19-years-old, but he has a terminal illness and he does not have much time left to live. He leaves the hospital and goes back to high school. There, he falls in love with Soo Min.