Is Insomnia hereditary?

It's a question that's been on my mind alot of late.
You see I don't sleep..much.
I regularly get by on just 3 - 5 hours a night for weeks on end.
I'll occasionally have a couple of what I call 'crash days' where I'll sleep closer to the conventional 8 hours.
On those days I usually feel worse than on my non-sleep days.

The thing is though my sister is also an insomniac and so, until a few years ago, was my Dad.
Are there others who have insomniac families or is my own a rarity?

I joke with people that were descended from vampires. ;-)
Well...at least I HOPE it's a joke....though I do love my rare steaks ;-)