What is the word for mourning something you never had? I'm looking for a word similar to "Schadenfreude" or "Sonder" in that it represents a very specific emotion. You dont get this feeling from an event, but rather from the implications of it. Say for example, your only sibling dies. This feeling comes from realizing you will never be an aunt/uncle, or from realizing you will have to organize your parents' funerals without your sibling's help. You are mourning the kinds of things you didnt know could be taken away from you. Anyone have a word for this emotion?
Though a bit broad, the word "melancholia" or "melancholy" can be defined as of a feeling sadness, mournfulness or lamenting with no obvious reason. I think that can include reasons never fulfilled or experienced - deeply rooted unrealized experiences.
My suggestion would be
Sorrow which covers both a sense of loss of the subject and the consequences thereof. As defined in 1b from MW
1a : deep distress, sadness, or regret especially for the loss of someone or something loved
b : resultant unhappy or unpleasant state //to their great sorrow they could not marry
I agree the dictionary definition is not a good context for the question so given the above.
For example, your only sibling dies. This sorrow comes from realizing you will never be an aunt/uncle.
Hiraeth? - a Welsh word that has no direct translation
According to Wikipedia, the closest available English translation is homesickness or nostalgia.
Hiraeth (pronounced [hiraɪ̯θ]) is a Welsh word which means 'nostalgia', or, more commonly, 'homesickness'. Many Welsh people claim 'hiraeth' is a word which cannot be translated, meaning more than solely "missing something" or "missing home." To some, it implies the meaning of missing a time, an era, or a person. It is associated with the bittersweet memory of missing something or someone, while being grateful of that/ their existence. Hiraeth bears considerable similarities with the Portuguese concept of saudade (a key theme in Fado music), Galician morriña, Romanian dor, Russian toska (тоска), German Sehnsucht and Ethiopian tizita (ትዝታ).