Does anyone know which Greek Myth involves human twins and female goddess?

I am looking for either a greek or roman story of a goddess (one of the well known ones like athena maybe) and something happens. Anyway the human mother does an act of some kind that either helps the goddess or is positive. Then the human mother is granted a wish. She asks the goddess to save her children (I think they are twins) from any kind of painful life or along that line. And the goddess kills them there and then as life is filled with pain and the only way to escape is to die. This has BUGGED me for years as I cannot ever find it. It might not be well known. And as a THANKS here is a fun quiz. http://tests.matchdoctor.com/567/Greek_Goddesses.html