Aleksey sits next to 4 phonetic neighbors — Alexei, Alexis, and Aleksei are the closest matches by sound. Most share Aleksey's Russian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"defender of mankind"
"strong, healthy"
"God has given"
"my judge is God"
"famous destroyer"
"firmness, constancy"
"China, land of the Khitan"
"brave, manly"
"merciful, kind"
"divine gift"
"defender of men"
Similar sound: These names share phonetic patterns with Aleksey — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Aleksey.
Rhythm: Aleksey is a 3-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.