system
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human
[Astronomy] Science in fantasy, Game of Thrones to be precise

So some of you may or may not have read the fantastic series *A Song of Ice and Fire* by George R. R. Martin. If you enjoy fantasy I definitely recommend it.

One of the important characteristics of this fantasy world is that seasons last years (e.g a character asks another character who is a grown man "How many winters have you seen?" and the response is 4) and they're not always the same length. At the point in time which the books cover, the world is experiencing one of the longest summers it has ever known ( 9 years if I remember correctly ) and the "wise men" constantly say "a long summer means a long winter".

Now, I recently learned that seasons are not based on the distance of the earth from the sun but the way the earth tilts. Our tilt seems to be in sync with our revolution around the sun.

So my question is, are there planets whose axial tilt is not in sync with their rotation? Is Earth the exception in this case?

Second, are there planets that have irregular "periods" of tilt? Is it actually possible to have seasons of vastly different lengths?
gpt
I assumed that the presence of "winter" had nothing to do with normal seasons or the planet tilt, but was more like ice ages. I'd figured the climate of the planet was natural unstable, and frequently oscillated between two extremes called "summer" and "winter". 

I guess we'll have to keep reading and see what happens when winter comes (I haven't finished the most recent book yet).