"Teacher Li has two younger brothers."
Why 两个 is correct but 两 is not?
Is it because you need to explicitly tell thst you are referring to individuals (doing it with 个), or am i wrong?
Because you need a measure word between the number and the noun.
两弟弟 is grammatically correct, but it is rare. However in spoken Mandarin, 两个 can be contracted to 俩 liǎ, thus you can say 俩弟弟.
Talking about quantity you will always need 个or a similar word, 只for animals, money is another one. That's why you say 两块.
Also, see my comment in another discussion: https://www.duolingo.com/comment/25256926$comment_id=25409028
I wouldn't use it, only when referring to the whole family, or the whole population.
No it would be false.. You only use "kou" if you re talking about some people.. However, if you re talking about your little brother you use ge.
I get we're supposed to use 两个, but wouldn't "李老师有二个弟弟" also be acceptable?