More details are needed about dizziness
to find out the cause of it.
If it is a mild imbalance(not a true rotatory feeling) when he moves his head or walks, present all days, without hearing problem or noises in ear, then it could be secondary to sinus problem affecting through eustachian tubes.
But if it is sudden, repeated, true rotatory spinning spells and/or associated with hearing problem or noises in ear, feeling like vomiting
or vomiting itself, diarrhoea
then it may be due to different causes.
If he gets a true fainting
then it points to heart or blood vessels related issues.
His father having tubes in ears or gioblastoma have no relation.
For proper diagnosis, management of dizziness and treatment of sinus problem you show him to a good ENT specialist