We have to also respect the fact that Jae has said he isn't that interested in talking to his brother.
Some family situations are like that.
I never had much interest in meeting with my father from the time I was a young teen and he gave no indication that he was interested in talking to me. (The evening before I left home in a small village in NB at age 17 to look for work in Montreal, my dad went next door to say good-by to their son who was joining the armed forces. I had told him earlier that I was going, even got him to sign for me to get a railroad pass for the trip, but I didn't bother to remind him.) Most years I would go home on vacation to see my siblings and friends. I was polite to Dad, the hello, how are you type of thing, but we never had a real conversation. I did take my babies to see him, but by then he had remarried (to a girl younger than me) and had small children of his own). He died a few years later. Seelerman and I were living in Ontario then, we went back for the funeral because it was the right thing to do and to be there with my sisters and brother. I don't think either Dad or I felt estranged / just indifferent.
If Jae has no interest one way or the other in keeping in contact with his brother, and his brother didn't call back when he didn't get through the first time, then perhaps they are contented on both sides. Though maybe his mother would like to be in touch with her son and might appreciate Jae's help in making a call. On the other hand, if Jae and his brother are unhappy with the situation, or have unresolved issues, the only way to handle it is to try to get in touch and maintain contact.
Seelerboy called us four times on Christmas day before he caught us home.