Yes, they are. But I am a loyal Lannister for some reasons:
Firstly, their sigil is the lion, which is one of my favorite animals since I watched The Lion King for the first time back in 1994;
Secondly, there is a theory in astrology concerning the Southern Hemisphere, in which there are actually six bipolar signs (Aries/Libra, Taurus/Scorpio, Gemini/Sagitarius, Cancer/Capricorn, Aquarius/Leo, Virgo/Pisces. When someone is born on November 3, for example, he will be a Scorpio regardless of the Hemisphere in which he was born. However, if this person was born on the Southern Hemisphere, he or she will have Taurus' traits. I, for once, am Aquarius, but since I was born in the Southern Hemisphere, I have Leo traits.
Finally, the Lion is one of the animals which represents both fire and Summer, the latter which is the season in which I was born (and the Westerlands lay in southern Westeros).
Then you have to choose a side, because the two of them are a bit antagonistic towards each other (the Wardens of the West must protect the Westerland from the pillages of the Ironborns). My favorite is Lannister.