Roy sits next to 3 phonetic neighbors — Roya, Joy, and Rowan are the closest matches by sound. Most share Roy's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"red"
"gentle, mild"
"from Leicester; possibly heavenly"
"horn, strength"
"narcissus flower, sleep-inducing"
"the white, noble one"
"worthy of admiration"
"champion"
"luminous, shining (via Lucinda)"
"fortress city, military camp"
"variant of Chloris, goddess of flowers"
"nobleman, chieftain"
"Noble and famous"
"of Rome, Roman woman"
Similar sound: These names share phonetic patterns with Roy — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Celtic origins, giving them the same cultural heritage as Roy.
Rhythm: Roy is a 1-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.