YOU SAID:
I have 2 sisters 3 brothers and 4 cousin
INTO JAPANESE
私は2人の姉妹が3人の兄弟と4人のいとこがいます
BACK INTO ENGLISH
I have two sisters and three brothers and four cousins
INTO JAPANESE
私は2人の姉妹と3人の兄弟と4人のいとこがいます
BACK INTO ENGLISH
I have two sisters, three brothers and four cousins
INTO JAPANESE
私は2人の姉妹、3人の兄弟と4人のいとこがいます
BACK INTO ENGLISH
I have two sisters, three brothers and four cousins
That didn't even make that much sense in English.