Is an outsider perspective allowed? I have 2 older brothers close in age. My oldest brother has very superficial relationships with his "friends". In German, he would call these types of people "Bekannte" or "Leute mit denen ich rausgehe" (people I hang out with).

He is in general quite closed up and I can remember that he had a sharp change of heart when he was about 16. For a reason that he won't disclose. When you ask him about anything that would need any type of reflection on his part it's typically "I don't know" and "Why do you ask?". His friends are similar and when someone tries to talk about something more personal you can feel the awkwardness and it's usually shortly discussed then brushed aside with a joke to change topics.

My other brother has actual friends. They buy each other gifts for their birthdays, call each other when something happened and they need advice or vent. Just "normal" stuff from my perspective.

Interesting things I've seen over the decades I studied them: In oldest brothers people-group the wives and girlfriends don't really mix with their husbands/boyfriends. They mostly meet separately.

My older brother is much more irritated when my other brother asks him about personal stuff than when I do it.

I don't think he talks with anyone about how he's feeling, apart from his nervous breakdown each year on Christmas.