míng / zhī / dào / tā / men / yǐ / jīng / xiāng / ài / tā / hái / héng / dāo / duó / ài / shí / zài / bù / hòu / dào

明知道他们已经相爱，他还横刀夺爱，实在不厚道。

Knowing they were already in love, he still stole his friend's partner, which was very dishonorable.