could be a cause of intracranial bleed and also it can be familial. Condition which comes to my mind when you say of headache, white matter
nodules and family history is CADASIL
. Its a relatively rare disease. Tests are available for confirming it. However before jumping on to all that, your brother's disease needs to be confirmed first. His scans also have to be reviewed. Correlation of findings in him and in you can give some conclusive evidence to the doctors.