Second, The Windy Summer was written by JJ Lin when he made his debut in Kym. "Looking for Love" and "Waiting for Love" were later endorsed by them, but now they don't endorse (maybe the advertiser asked for a change), so naturally there is no cooperation, and Kym is also very successful in music now, and she doesn't need her senior brother to help her out.
Third, you should know that JJ recently moved to Warner, and Kym is still in Ocean Butterfly. Companies are different, unless artists themselves request cooperation with artists from other companies, it is difficult to cooperate.
The first time JJ spoke to Liao Jun ("confession"), including Charlene Choi's "dimple", I was also very angry. JJ asked for cooperation, and I was calm. JJ didn't take Kym, because Kym is very good now and doesn't need help.