Okay. Let's see how good your advise was. Let's say your brother bought a single Gold 1 Ounce Kruggerrand at the year low price of US$1,192.75. Gold price today is US$2,337.00 today. So well, done he doubled his money, if he sells that 1 ounce coin today. Impressive.
So, if he rather listened to someone who knows about investing, he could have placed that US$1,192.75 in the SPY stock in the US on 1 January 2013. Maybe he decided not to re-invest dividends, in which case today, he would have had US$4,897.40.
If he clicked the button to reinvest the dividends, that US$1,192.75 would have grown to a full US$5,413.70 today.
You are free to go do the math on
https://stoculator.com/, where you can actually see what you would have made with your money.
Again, Gold is not an investment. It is a very long term investment and should form a very small part oof your portfolio. Use gold only as a safe haven when the markets struggle.