Is it grammatically wrong to say consist of instead e.g. 5 boys and boys?

It's not grammatically wrong to say "consist of" when listing multiple items, but it's not the most common or idiomatic way to express it. Here's why:

* "Consist of" typically describes the components of a whole. For example: "The team consists of five players."

* For lists, "include" or "contain" are more natural. For example: "The team includes five boys" or "The group contains five boys and three girls."

So, while "The group consists of five boys and three girls" is grammatically correct, it's a bit awkward. "The group includes five boys and three girls" or "The group contains five boys and three girls" sound more natural and are more commonly used.