This is the 4348th most frequent Arabic word.
منهم
"منهم" means "from them" or "among them" in English.
In this sentence, 'منهم' refers to 'among them' (the gifts bought). It specifies that one of the items was a book.
اشتريت هدايا وكان منهم كتاب رائع.
I bought gifts, and among them was a wonderful book.
Here, 'منهم' is used to highlight a subset (new students) within the general group (students in class).
في الفصل طلاب كثيرون، ومنهم طلاب جدد.
There are many students in the class, and among them are new students.
In this context, 'منهم' highlights an individual (my brother) within the group (those who passed).