The Otherhearted are people who feel a strong familial connection to a species or animal. Unlike otherkin or therians, they do not identify as the species in question, however feel a deep emotional bond to them. Someone who is hearted to a species will usually refer to this as their "heart-type". Likewise, they may refer to themselves as (insert species)-hearted.
Having a heart-type is more than simply liking a certain species a lot, it is significant enough to make up part of the individual's identity. It does not equate to having a favorite animal, but rather that the feeling invoked by the creature is akin to that of a family member or close friend. When someone sees or thinks about their heart-type, they feel an in-explainable bond and immediate connection.
Its important to realize the difference between being Otherhearted vs Otherkin, comes down to "identifying with a species" rather than "identifying as".