"My relatives are very rich."
Translation:Họ hàng của tôi rất giàu.
It comes naturally to me since I grew up speaking Vietnamese, but I didn't quite know how to describe it. Someone else described it very well and improved my understanding. If it involves singular words, you can drop the của. "Mẹ tôi", "xe tôi" (my car), etc. However, if it involves compound words like "họ hàng" it naturally follows with của tôi. Of course, you could omit của anytime really, it's colloquial and depends on the context. This isn't a firm rule. It's textbook. Just shows how beautiful languages are with many different ways of expression =)