Why are FP+ times available for someone else, but same times don't show for me?

[jar]

I'm confused as to why my brother and I (separate reservations) are shown different FP+ availability for the same # of people on the same day.

I selected a date in mid-December. I have a reservation for 2 for BTMRR and want to move the time to different slot so it is adjacent to another FP+ reservation I have (it would not overlap, but I want them to be adjacent). MDE is not showing me that slot available (I do not have any conflicting FP+ reservations that would make that slot unavailable). But if my brother logs on and seeks a reservation for 2, MDE shows him the slot I want.

Anyone have any ideas?