I was curious, since I hadn't heard of them before.
While the House of Hapsburg draws its name from a castle, I thought it might be possible just thinking out loud to have a very loose definition of "Empire,' based not on conquest but on members of one royal family ruling several countries.
However, the problem is that there doesn't seem to be a way to get the ruler of one of these to become, say, King of the Franks after Chrlemegne. While there was a Duchy created in the same area as the capital later, since - if I'm reading right - it went by a different name I don't think that qualifies.
It became a Margraviate under the Frankish Empire in 828; local rulers were deposed for followign an anti-Frankish rebellion. If - and this is a big if as I don't know why they followed it - they help to put downt he rebellion they might wind up with some power with an ATL Holy Roman Empire, but getting them to be Emperors would be well-nigh impossible, and I don't know enough about the way the Hapsburg ruling family grew to say whether these rulers could spawna bunch of rulers of different lands.
But, even that wouldn't be most peoples' definition of an empire, in the way you seem to be describing. And, they'd likely have to do some incredible work and also rely on a lot of luck to get anywhere near Hapsburg size, anyway. (Hapsburg rise osn't ASB, but it is one of those things where you can see quite a bit of luck, such as royal families dying out and inheriting a number of places.)