The problem of love.

If that's the case, you'll have to play hard to get. The closer you are to him, the farther he is from you. If you want him to be near you, come at a reasonable distance. If he is really interested in your sister, he will naturally go to her. If you are not interested, any of your efforts will be in vain. Another way is that people with the same interests will have more topics to talk about together.