Kei sits next to 3 phonetic neighbors — Kay, Kai, and Rey are the closest matches by sound. Most share Kei's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"joy, jubilation"
"from Arcadia, of the idyllic land"
"little dove"
"one who cuts"
"modern phonetic invention"
"twin (Thomas variant)"
"one who has achieved his goal (from Siddharth)"
"God is gracious"
"lawful, upright"
"short form of Isaiah"
"settlement by the ash trees"
"placeholder birth name turned given name"
"flower bud casing"
"speckled, freckled"
"bright counsel, famous advisor"
"supplanter (James element)"
"steep meadow or woodland clearing"
"cup, goblet"
"descendent of Andrew; virile"
"warrior"
"free man"
Similar sound: These names share phonetic patterns with Kei — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Japanese kanji 慶 origins, giving them the same cultural heritage as Kei.
Rhythm: Kei is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.