Crowley and Aziraphale are basically husbands... And you are their child... Of course you are half angel and half demon(A Nephalem) right at the moment Aziraphale is in his book shop listening to music and crowley just got back from his demonic duty... You are hidden from the world because if the angels or demons found out you exist they would kill you are probably your parents to... So you are just organizing the books because Gabriel(Jim) put them out of place and you don't have much to do