Sons of Demeter:

Plutus/ Eniatus (with Iasion)

Philomelus/Bootes (with Iasion)

Korybas (with Iasion)

Areiôn, immortal horse (with Poseidon)

Eubouleus (with Karmanor)

Demeter's children were Persephone (with Zeus) and Plutus (with Iasion).

At the marriage of Kadmos and Harmonia Iasion was lured by Demeter away from the others and later killed by Zeus.

Iasion

Yes, Demeter is mother of eight children.

Persephone (with Zeus)

Ploutos (with Iasion)

Bootes/ Philomelus (with Iasion)

Korybas (with Iasion)

Eubouleus (with Karmanor)

Khrysothemis (with Karmanor)

Despoine (with Poseidon)

Areion (with Poseidon)

Artemis is also at times called a daughter of Demeter.