Marwan sits next to 2 phonetic neighbors — Merwan and Marwane are the closest matches by sound. Most share Marwan's Arabic-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"hard stone, small sharp rock"
"devoted one"
"plural of noor (light)"
"blue"
"guarded place"
"handsome, beautiful, graceful"
"handsome, cheerful"
"knight, horseman"
"breaker of obstacles"
"holy, exalted"
"red earth, ground"
"one who judges justly"
"beauty, grace"
"letter Z sound"
"shining light"
"most honorable"
"one who is complete"
"luxuriant, full of life"
Similar sound: These names share phonetic patterns with Marwan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Arabic origins, giving them the same cultural heritage as Marwan.
Rhythm: Marwan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.