Kadarius sits next to 3 phonetic neighbors — Darius, Kadaris, and Arius are the closest matches by sound. Most share Kadarius's Old Persian via Darius-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"he who holds firm the good"
"pledge, oath"
"island"
"God is my judge + priceless/flourishing (Dan + Anthony)"
"absence of subjection or constraint"
"spear ruler, spear power"
"slender, narrow"
"little warrior"
"charcoal hill"
"hay valley"
"noble, dignified"
"of Mars, warlike"
"worthy of being told in stories"
"small songbird of the meadow"
"companion, friend (Old English origin)"
"forest dweller, one of the wood"
"Wealthy, prosperous warrior"
"valley of Wendel"
"rye farmer"
"good, excellent + blue"
Similar sound: These names share phonetic patterns with Kadarius — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Old Persian via Darius origins, giving them the same cultural heritage as Kadarius.
Rhythm: Kadarius is a 4-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.