AH :
Hou denied wrongdoing and pinned all the blame for getting seduced on FFYY and she didn't say anything so she got nearly all the blame. Hou was exiled iirc? The elders wanted to kill FFYY, but TSJ wouldn't let them. She suggested offering herself (her blood or energy? I can't remember which) to the clan's fox spirit, which was basically a horrible way to die slowly. But TSJ later helped her fake her death and reconnect with her son after she suffered for a bit.
I was just thinking that maybe FFYY killed Hou as a way to make it up to Jing for all the things she did to him. She knows that Jing is too kind and will never kill his brother. And with Hou still alive, he will find ways and means to torment Jing. So killing Hou frees Jing from his nonsense to enjoy his life with XY. As for YY, she loves Hou too much to live without him, so she kills herself with him.
Sighs...Hou is the worst! I wished Tong Hua could have given him some painful punishment. Death by arrow is too easy on him. He deserves the same torture he gave to Jing x 100 years.