Analysis on Feng Xin and Jian Lan
Feng Xin took an interest in Jian Lan when he saw her stand up against the rebels. After XianLe's downfall, he started paying for nights with her just to talk. (Feng Xin is a gentleman after all, and Jian Lan is said to have teased him about it.)
Mu Qing was gone, and even though they were rivals, he was still part of the trio. Xie Lian was once again haunted by Bai Wuxiang, when he returned home he was always in a bad mood, stressed and not talking to anyone. The only person Feng Xin talked to as an equal at that time was Jian Lan.
FX and JL were survivors of a war, they were living through a dark period, but they found each other and supported each other emotionally.
However, as XL himself realized, FX lived for XL, he grew up being brought up to obey him and put his life above his own, and Jian Lan noticed. FX needed to learn to let go of XL, but by then his relationship with JL had already become unsustainable, and in the end FX had neither the prince, nor the woman he fell in love with, nor his rival.
This phase of Feng Xin's life was extremely important for him to realize how much he placed Xie Lian's life at the center of his universe and to overcome this, it was important because he, after everything he had gone through, finally had moments of peace and happiness (the latter also applies to Jian Lan) and, in the current line of TGCF, it was important for him to realize the family he could have had, but lost due to his own immaturity.
At the end of TGCF, JL says to XL that his time with FX was great, but it's not time he would ever go back. They were both good for each other when they were together, but it didn't work out and it wouldn't work out in the current TGCF lineup.
Feng Xin is much more than an easily stressed character that only serves for headcanon and fanfics with Mu Qing, his life was not just the XianLe trio and his relationship with Jian Lan not only proved that, but served to develop it.













