It will be practically impossible to get your brother as a dependant relative. The bar for an adult (and he is an adult, as he is over 18) dependant relative is very high.
- The applicant must, as a result of age, illness or disability, require long-term personal care: that is help performing everyday tasks, e.g. washing, dressing and cooking;
The applicant must be unable, even with the practical and financial help of the sponsor, to obtain the required level of care in the country where they are living because it is not available and there is no person in that country who can reasonably provide it, or because it is not affordable.
The Entry Clearance Officer (ECO) must be satisfied that the applicant will be adequately maintained, accommodated and cared for in the UK by the sponsor without recourse to public funds. If the sponsor is a British citizen or settled in the UK, they must sign a 5-year undertaking to that effect, at the entry clearance stage
https://www.gov.uk/government/uploads/s ... FM-6.0.pdf
You can of course help him come as a student or help him get a job with a sponsoring company as a Tier 2 employee, but not as your dependant.