Kellen sits next to 4 phonetic neighbors — Kellan, Kell, and Helen are the closest matches by sound. Most share Kellen's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"slender, narrow"
"son of the marsh dwellers"
"olive tree"
"shining with fame"
"from Mauritania"
"the promised land"
"free man"
"near the holly trees"
"Yahweh has shown favor"
"city of God (alternate interpretation)"
"great fort, spacious hill"
"God heals"
"small, junior"
"father of light"
"ancient, enduring"
"goodness of Yahweh"
"born of fire"
"noble eagle (adal + aro)"
"he who holds firm the good"
"joy, laughter"
"ancient, enduring"
Similar sound: These names share phonetic patterns with Kellen — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Irish Gaelic 'caol' origins, giving them the same cultural heritage as Kellen.
Rhythm: Kellen is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.