Birth secrets and enemies

Hi!
I would like to watch some drama or movie with birth secrets or the discovery of dark secrets of the main character's parents. More or less I am looking for:
- Enemies who find out later in the story that they are relatives by blood. They might be father-son, father-daughter or brothers.
- A son or daughter investigating a crime or fighting against some dark organization find out that their nearest relative who they trust is behind everything.

Some examples would be either Queen Seon Duk or [spoiler] Beautiful Gong Shim, in which a man helping a woman find his long lost grandchild finds out he is actually the grandchild.[/spoiler].

I would like movies or short dramas (16-24).

Thanks you :)

Disclaimer: I am aware that I am asking for spoilers. I don't care, but please anyone reading this thread be aware that this post might or might not be mined with spoilers :)

I Remember You
East Of Eden
likit fah cha ta din
Can You Hear My Heart
maybe the bridal mask also fit what you want
yeah i know they are not short but they fit exactly what you want

Many thanks!
Triangle seems to be exactly was I was asking for.
@Safae, by I Remember You do you mean the 16 episode drama starring Seo In Guk and Jang Na Ra?
I've already watched Can You Hear My Heart and Bridal Mask, I enjoyed both of them.
I tried Shining Inheritance once and didn't get into it, but since you recommended I might try it out again one day.

@kestrel yes
also east of eden has a birth secret