I think a much better and long term idea is to expose him to Hashkafa Seforim. Derech Hashem, Ikkrim, Akeida, Abrabanel and Maharal. These can take over a person. Instead of musing, he can enjoy these very enjoyable Seforim. If he does well then he can appreciate Seforim. That much is my experience.
Even before that, there is Medrash and other non-Gemara sefarim that not necessarily would a Yeshiva boy bump into, or as in my case, nor would he be encouraged by the pro-regulars.
I do have to say that being that he is a brother it does change the picture. Siblings can have all types of conversations; this doesn’t have to avoided.