According to the traditional geneaology of the Greek Gods, Cronus had six children with Rhea: Hestia, Zeus, Hera, Poseidon, Hades and Demeter. All children were part of at least one major variation of the Twelve Olympians and - with the exception of Hestia - had temples honouring them.
Hestia was Cronus firstborn and her sanctuary was the hearth of the Prytaneion, the political and religious center of the community. Also, Hestia was thought of as being present in every offering fire in all temples and received first offering in sacrifices. Thus, she didn't need temples of her own.
Of course there may have been temples honouring Hestia that we simply don't know about. After all, absence of evidence is not evidence of absence.