Degree of nobility

For nobles, the order of distinguishment goes duke, marquis, count, viscount, baron, baronet.

Mores
Generally nobles could not oppose to higher level nobles.

During gala parties, it's usual that the guests dance, but only in degree order. The higher degree nobles dance first, followed by the lower degree ones.

It's also usual nobles get marriage with another nobles, but it's possible nobles get marriage with commoners.

The main protagonist noir has the noble rank of baronet.

Trivia

 * It's not stated on how nobility rankings work should someone marry into a higher or lower ranked House. Though it's possible if a House only has one heir, the lower ranked noble inherits the higher ranked House's name.
 * Since Noir (Baronet rank) and Emma (Baron rank) are genuinely in love, with marriage a definate future for them and there being no mention of Emma having siblings, this brings the future of the Brightness bloodline into question.