Science fiction set in future in america where the land is partially under water + brown hair female chracter and blond hair male character

[Taejeong]

-I read this around 2017-2019 and seemed pretty new
-set in future parts of America are underwater but not all
-in the beginning of the book, the brown haired lead character was pulled out of school by her brother who I think is in the military
-blond boy lives in the poorer section of the country and around the middle? end? of the book his house is lit on fire from a gas leak
-near the end of the book the blond guy loses his memory and is admitted to the hospital
-there is a part of the country that is far more advanced and the blond character lives there after his memory loss for treatment for his brother who I believe had glasses
-the blond character was in the sewers for some reason at the start of the book

[Rainbowheart]

Does anything on the Drowning Towns list look familiar?