I have chronic migraines lasting weeks to months. no immediate or past family history of migraines, however all 3 of my children developed them in grade school (we frequently have them at the same time). could this be familial hemiplegic migraine?

There are specific criteria for the diagnosis of Pediatric migraine headaches. Ensure that your children have no ongoing infection, no fever and no vomiting. If these symptoms occur, please see acute care. Watch for neck stiffness and, discuss treatment with NSAIDs with your pediatrician.

Migraine has strong genetic links and does run in families, such as yours. Hemiplegic migraine is a rare variant associated with focal paralysis. It appears you may have a tendency for "chronic daily migraines", and would suggest you take preventative medications, and there are many excellent choices. See a neurologist, and have your children also see a pediatric neurologist.