People who are related belong to the same family.
The children, although not related to us by blood, had become as dear to us as our own.
这些孩子虽然与我们没有血缘,但却变得如同我们亲生的一样亲。
If you say that different types of things, such as languages, are related, you mean that they developed from the same language.
He recognized that Sanskrit, the language of India, was related very closely to Latin, Greek, and the Germanic and Celtic languages.
他认识到梵语,即印度的语言,与拉丁语、希腊语、日尔曼语和凯尔特语有着密切的同源关系。