Hey @-_g2zi1tdues, thanks for writing!
You can definitely invite your brother to join your Premium for Family plan.
Since he's not actually moving to a different country, you don't have to worry about the Premium for Family plan not working or stopping.
As long as all users share the same physical address, you'll be able to travel and even stay extended periods of time overseas and you'll continue to have access to Spotify as usual.
Just make sure to send and accept the invite in Malaysia.
Let me know if you have any other questions 🙂