since go ahead, I have a big problem with "the mother". for me, she's so bad and despicable that sometimes I can't watch her scenes (the actress are good, tho) because make me feel so angry about she treats her son. that's not okay. what do you guys think? 

Both for sure! This character talks about struggling with depression when her children with her first husband were young and clearly has some sort of mental disorder like Borderline Personality Disorder. Mental illness does not excuse abuse, however, hence why she is also evil. Her cruelty, manipulation, and mind games were absolutely a choice and she knew full well the harm she would cause her son. That was the point. The actor that portrays that character is phenomenal—to the point I could see her getting hate mail, because she channels that twisted character so well. 

She never healed after losing her daughter. The show doesn't share if she ever went through therapy which was a missed opportunity to promote mental health in Korea. Unfortunately she could never see that others were also hurting. That is why San Ha's lines were important at the end where he says he should have told her. She kept thinking she was the only one who cared about her daughter and that is what made her intolerable.

She is unwell.  My mother, a manic depressive-depressive, was similar.  Unfortunately, based on my observations during the four and a half months my mother was being treated at the US National Institute of Mental Health, therapy in and of itself doesn't help.  Various medications helped to tone down my and the other patients' manic/depressive behaviors whether manic or depressive.  Group sessions and one-on-one counseling only seemed to exacerbate the negative aspects of the root chemical imbalance each of the patients shared.    I loved my brilliant, genius mother dearly, hated and feared the emotional, mental, and physical abuse meted out to me and my brother, yet hated even more watching the agony she experienced with each and every mood swing that occurred with no warning.   I didn't know what maternal love was, which was admittedly difficult during my growing years.  I knew there was nothing I could or would have done to deserve the abuse or lack of maternal love.  

I found myself crying throughout most of this show.  It was hard re-living my own experiences during this well-acted depiction of something I struggled to understand and live through until my mom ended her lifetime nightmare four days after her 62nd birthday.  But, it is very important for everyone to face the reality that does exist; mental illness does not equal evil.  Mental illness is a hell for the person who has it, and is a constant heartbreak and worry for those who endure the collateral pain and damage.  

 ValLB:
It was hard re-living my own experiences during this well-acted depiction of something I struggled to understand and live through

I'm sorry that you lived through something that horrific. And as children, we really don't have the capacity to truly understand what's going on around us when the adults who are supposed to be protecting are harming us instead. In Family by Choice, I think San Ha's mother is unwell but still has the capacity to determine right from wrong and act upon it. I say this because she treats So Hui impeccably. I suppose that could be part of her illness, where So Hui is the replacement child and San Ha is the blamed child. 

I had a difficult time when viewers minimized Hae Jun's pain of being abandoned by his mother who promised to return for him. My mom literally threw a birthday party for her youngest child (age 2) then disappeared that night. For years, whenever I saw anyone who may have looked like her, I would look again just to make sure it wasn't her. But the truth is we weren't allowed any photos of her and after a while, I didn't really remember what she looked like. I didn't yell, "Eomma" to a stranger like Hae Jun did, but I felt myself constantly looking for her wherever I was. And that feeling of abandonment affected my ability to trust that any partner would actually stay. 

San Ha, Hae Jun, and to a certain extent, Joo Won got dealt a bad hand in the maternal department. This series didn't sweep the difficult parts under the rug. There were many episodes I cried with or for the characters. But the show also showed us their capacity for joy and their resilience. Kudos to the actors for their incredible acting and giving us a great drama.

Our emotional struggles, though caused by very different circumstances, are not unlike what we watched in this drama.  We were both abandoned -- you literally, me figuratively -- left to long for the maternal love and warmth we each deserved, but were denied.  It is no wonder that we identified with the characters and the mark they left on us is a testimony to the excellence of the writer/s and actors.  The best we can do as we live out our lives is to believe in ourselves and to be everything our mothers could not be.

Agree that the actress was superb as she played this role so well we dislike her intensely.  As a mother myself I'm appalled at any mother who would do something like this to their child.   Yes, she was ill, but that illness made her son's life hell.   She left when he was 9 without a backward glance to her child who was hurting and when she was good and ready she came back to him as an almost-adult to hurt him some more.  He then, selflessly, gave her 10 years of his life to care and look after her.  (Her brother should also be taken to task over this as she shouldn't have been her abandoned son's responsibility).  Much longer than she had raised him for.   Thankfully he found it was all psychological and started to pursue his own life and happiness.    

My birth mother left me when I was about 8 and made contact again when I was 16.   By that time my step-mother was my mother and although I met my birth mother, spoke with her on the phone and she even, eventually, came to stay a couple of times to spend time with her grandchildren, I never fully reconciled with her - she was always a distant aunt sort of figure.  And I was fine with that.   She had to live with her choice and its consequences.

I have marveled and been very upset over the years when we in the US have to hear stories supporting the supposed fact that abusers and or absent parents are always male.  Isn't it amazing and emotionally vindicating that a drama -- Korean, not American -- dealt with the reality of abusive and or physically or emotionally absent mothers many of us experienced firsthand throughout our lives?  

You, like my daughter, were fortunate to have a step-parent to fill-in as a parent.  My daughter's father didn't abandon her and loved her dearly.   He remarried after we divorced, then moved to the middle of the country, unable to see her as much as they both would have liked.  They adored each other, but she needed a reliable, physically present father figure who was willing to "stand in" as a dad.  After her father died 20 years ago, she was very grateful she had accepted her "dad" many years before.  Her biological father was grateful too and made a point of thanking my husband for "being there" as a "dad" and asked him to continue loving my daughter after his upcoming death.  But, it sounds like your mother abdicated her role of mother long ago, yet wanted your children to at least know they had a grandmother.  Viewing her as a distant aunt sort of figure makes sense to me, especially if that is emotionally gratifying for you.  As for her, I agree "she had to live with her choice and its consequences".  

Yes VakLB, I was fortunate with my step mother.  I am glad your daughter had the benefit of a step parent who loved her as well.     I couldn't ignore the fact that I was related to my birth mother but I certainly didn't feel close to her and I had to distance myself when she got suffocating.  Whilst she appeared to want to go back to having the daughter she left, I had moved on.  Eventually she realised my boundaries and respected them.      

Sanha though didn't have a mother figure at all, do two dad figures make up for that?  

Growing up with a non-maternal mother, and ultimately being the maternal, loving mother my mom couldn't be convinced me children benefit the most with a loving mom and a loving dad.  My dad was the most gentle, kindest, and loving fathers I have ever met, but no matter how hard he tried he couldn't inject the missing female touch.  He prepared me for puberty issues and for sex, better and more positively than most moms, but he couldn't offer the female touch my daughter needed and I was thrilled to provide.  The two genders together offer the child/children valuable and unique perspectives and guidance that one gender alone can only hope to offer.  

Two dads is certainly better than nothing, but Sanha instinctively recognized, as I know I did, that something essential was missing.

Surely it's an illness. We don't know much of her story - since the last few episodes were kinda slow and empty here in there, it would have been better to put hints why Sanha's mother is like this.

And did you notice it didn't start with the daughter's death. It was said the kids were left alone for 2 day (if I'm correct). She was having a hard time before.