Hi,
Dizziness even in standing position or during walking is concerning.
It could be due to variety of causes or it could be transient.
Does your brother has any other symptoms with this dizziness?
Perhaps if the dizziness is not troubling much then you may wait for few days.
Until then he may take proper hydration and electrolyte balance with some symptomatic antihistamines treatment like betahistidine.
Do not panic.
However if the problem is persistent, he should see a doctor at the earliest and get evaluated further. It can be related to
ear infection or some
allergy but here there are less chances.
I will suggest you undergo routine blood count,
ESR, blood electrolytes, tests for vestibular (balance) system like electronystagmography or rotation tests to diagnose the cause for dizziness.
Your local physician or GP will know about the test. He/she will can order the test after complete history and thoroughly clinical examination like temperature, pulse, blood pressure which will enable us to arrive a diagnosis.
Regards,