If an adult in your family applies on his own to live in Spain (to work independently, for a company, or just to reside while living on a foreign income) and obtains a visa, it will be relatively easy to get your brother in by having him apply afterwards for a “reagrupaci?n familiar” visa. This will allow your brother to stay as long as the other family member (mother, father, etc.) remains in Spain under the conditions of the original visa. From there, as a legal resident he will be able to attend Spanish schools.
If instead you wish to have your brother apply individually for a student visa you will need to contact your nearest Spanish consulate for more information. This will be a lengthier process for your brother, but would avoid the issue of getting another family member a visa and having to provide for them. Here is their contact information in Hanoi.