Mostly Fanfics
A Blog Type Book For Each Where They Can Just Vent
Mia is a Hufflepuff (Illvermony House: Horned Serpant) and a Libra.
Ella is a Gryffindor (Illvermony House: tbd) and an Aquarius. 
Both are children of Athena and (if you couldn't tell by the username) Herondales.