What is a genus in which seeds possess  two cotyledons and endosperm is not used up completely during embryo development and therefore remain persistent?

Castor is an exception.As it is a dicot but endosperm still persists in its mature seed.

Endosperm may either be completely consumed by the developing embryo (e.g., pea, groundnut, beans) before seed maturation or it may persist in the mature seed (e.g. castor and coconut) and be used up during seed germination