Dan,what is your little brother's name?
I am sorry,I don't know,because he can't speak,he is too little.
1.Has Dan got a brother or a sister?
2.Does Dan know his brother's name?
3.Why can't Dan's brother speak?
4.How old is Dan and how old is his brother?
5.Do you think it's right that Dan doesn't know his little brother's name?
6.Have you got a little brother or sister?
7.Do you know his or her name?
8.What is your little brother's or sister's name?

Dan has a brotherNo, he does notbecause he can't speak,he is too little.вот тут не знаю,точных указаний нетno it is notесли у тебя есть сестры-братья: yes, i have,а если нет: no i have notyes i do(если мелкий есть)his/her name is ( если есть)