一個句子能有兩個名詞子句嗎？ 例：It says that female and male brain are different and that they develop at different rates 裡有兩個that所以是有兩個名詞子句嗎 ？

一個句子能有兩個名詞子句嗎?

yes, as long as it makes sense but not verbose. Further, you may have 3, 4, 5, or more if you want.
Noun clauses are just like nouns. There is no limitation on the number of nouns in a sentence.

Nonetheless, "you can" does not mean "you should".

＞.As long as you put conjunctions between two nouns... 你講咩嘢"makes sense"...
沒醬子簡單的！兩個名詞子句在同一個一個句子裡面，不一定會玩弄同樣的角色．所以不一定會用conjunctions 來連接他們．

舉個例子來說吧：

<That she is dirty> does not mean <that she is not pretty>.

這句子哩，有２個名詞子句．一個是＜主詞＞，一個是＜受詞＞．他們之間也不會用＜conjunctions＞來連接的．

不過，為神是你ＰＯＰＯ提問？而不是　安弟　提問？

As long as you put conjunctions between two nouns... 你講咩嘢"makes sense"...