Boyfriend traveling to Vietnam with his brother

For context, I’m 20F and my boyfriend is 21M. We’ve been together for four years, and we’ve built a strong, trusting relationship. We’ve even traveled to Thailand twice in the past year, which was an incredible experience. I really admire the kind of partner he is—supportive, thoughtful, and genuinely trustworthy.

Recently, his younger brother (18M) expressed interest in traveling to Vietnam this December. I completely support it, and when my boyfriend invited me along, I told him that I felt it would be a great opportunity for them to spend quality time together—just the two of them. I want them to have that kind of memory, especially as brothers.

That said, I’d be lying if I said I didn’t feel a little conflicted. Before this trip idea came up, my boyfriend and I had talked about going to Vietnam for my birthday in September. We were really excited about it, but once his brother brought up his plan, my boyfriend seemed to shift focus. I understand—we're both college students, and juggling schedules and finances can be tough. But it still stung a little when the original plan faded away.

I don’t want to make this about me, and I believe that space is important in any healthy relationship. But sometimes, I can’t help the intrusive thoughts—what if he goes and comes back... changed? What if he comes back and doesn’t feel the same way about us?

I know these fears aren’t rooted in anything he’s done—they’re just the vulnerable parts of me speaking up. I trust him, and I trust what we have. But being honest with myself also means acknowledging that sometimes, even when you support someone wholeheartedly, there can still be a small part of you that feels a little left behind.