Spoiler!
Ok, I'm saying this because I read the novel and this translation is just bad. It's not just a picture. If it were that, would Ash look for it so much? That painting represents the love Ash's mom has for her husband, but the husband doesn't see it that way and thinks she cheated on him and that Ash is not his son. (He is)
And the husband in turn had an affair to get back at her. When his mom died, he got rid of everything that belonged to her and quickly remarried. Ash stopped smiling after that and the stepmom even berated him for not smiling. His dad ignored Ash's existence and he was raised by his sister and grandparents. The husband was a cheating bas**** and didn't understand how much she loved him because he could not get past his jealousy. He had a loving wife and children, but could not appreciate it because of his own stupidity.
And the husband in turn had an affair to get back at her. When his mom died, he got rid of everything that belonged to her and quickly remarried. Ash stopped smiling after that and the stepmom even berated him for not smiling. His dad ignored Ash's existence and he was raised by his sister and grandparents. The husband was a cheating bas**** and didn't understand how much she loved him because he could not get past his jealousy. He had a loving wife and children, but could not appreciate it because of his own stupidity.