1. Starting from some is an attributive clause, and who is the object of the relative pronoun, referring to "vegetarian". Since it is behind the preposition of (meaning "among"), it must be used Accusative case, some of whom means "some of them". Sentence Translation: There are many types of vegetarians, some of whom don't even eat animal products such as milk, eggs or cheese.

2. Another example: There are many students in our school, some of whom come from foreign countries. There are many students in our school, some of whom come from foreign countries.

3. You may ask: Since it means "some of them", why not use some of them? You can also use some of them, but you must use a period to separate it from the previous sentence, that is, There are many students in our school. Some of them come from foreign countries. English commas and periods cannot be replaced casually! A comma can only separate a main clause and a subordinate clause, or two parallel clauses, and only a period can separate two independent sentences.