Winry isn't Ed's cousin. She and Pinako are very close friends of the Elric family, thus Ed would call her "Aunt" or whatever they call her in the English version.
Anywho, this is one of my absolute favs ^^ The story is extremely well done and unlike many other anime shows, its not set in Japan, but in a place that looks like early 20th century England.
I actually quite liked the card system. Although, I can't really compare on the original Kingdom Hearts, as I have never played it on account of my lack of PS2. So I don't really know which one is easier.