lineage, bloodline
胄 centers on inherited family connection: lineage and bloodline, the line of descent that passes from one generation to the next.
胄 is composed of 由 (origin, reason) over 月 (flesh/body), suggesting the physical origin or fleshly descent of a family line. The exact historical development is uncertain, but the component combination fits the meaning of lineage.
The top 由 means origin or reason, and the bottom 月 is flesh. Picture the flesh-and-blood origin of a family: the lineage that connects ancestors to descendants.
For チュウ, imagine a family tree drawn in the center of a room: the central lineage cues チュウ (like 'chew' but with a 'ch' sound), and the tree shows the bloodline.