I gave some hundreds thousand satoshis to two of my brothers a few years ago. I explained the big picture without telling the details but I asked them to hold for a few years. Now, they are shocked seeing the value of the Bitcoin  in their wallet which was increased so high than the first time I gave them.

That makes them realize that Bitcoin can be more valuable in the future. I see they now add more satoshis to their wallet after Bitcoin hit $80k and with other coins. That is their choice but they are asking me if they don't understand. So the best way is you help them install a Bitcoin wallet, best is electrum on their phone, send some satoshis to them and say that they must keep it for a long time and let it be.