Answers
Every investor has to finance his investment through his own funds, which have to be transferred from his bank account abroad to his already opened Greek bank account. So the best solution is to proceed to a private loan agreement with your brother in your country, transfer the related amount in his account abroad, and consequently he will send the total amount in his Greek bank account. If the loan will be concluded in Greece, a stamp of 3.6% is applied.
The amount of money on his behalf must come from abroad, a Greece bank equity or private transaction. Each application to be supported needs at least the amount of 250,000 euros to get Greek Golden Visa.
Please have in mind that loaning of funds is not forbidden.
In any case, for any purchase of a property in Greece you will each need to pay at least the amount of 250,000 euros.
You can do the loan at your home institution and then he sends the whole amount to Greece. The important part of the whole transaction is that 250,000 is imported into a Greek bank account and, preferably, that the funds should come from the investor's bank account and arrive in the investor's bank account in Greece.
This is possible. The easier way is to transfer the money from overseas to his own Greek bank account. Otherwise, you will sign a loan agreement in Greece, which is taxed per 3.6%.