If it was just headache it wouldn't be so often. Migraines are sort of chronical headaches and i used a more general description for it what already shows that you don't know about it. Migraine attack i get roughly once a week, weak headaches which i can easily control way more often that's why i used that word. Doctors don't know exact reason on headaches/migraines that's why there is no real cure for it, just some drugs which can weaken symptoms, some body excercise, so you can't say it's family if reason is unknown. All that you would probably know is if anyone from your family would visit doctor. My family also get synchronized headaches like due to weather changes but it's something most people have so yeah, might be coincidence. Besides most people whine about weak headaches calling them migraines cause of lack of knowledge.
You would be suprised how many "headaches" there are, from back of head, front, from sinuses, presure feel, behind eyes, cluster headaches/migraines and i have luck to experience all of them. Especially strong cluster like headaches for 24h or more. My personal record is 2 weeks coninous pain so far \o/