Astro sits next to 3 phonetic neighbors — Castro, Cosmo, and Orion are the closest matches by sound. Most share Astro's Japanese cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"star"
"eagle friend"
"little fiery one"
"little fire"
"powerful leader"
"remembered by God"
"modern invented name"
"vision, dream"
"protector of mankind"
"little red-haired one"
"boundary, border"
"rocky land, gray land"
"immortal, deathless"
"gate attendant, herald"
"deer meadow"
"a crow-like black bird"
"great, supreme, exalted"
"most high, exalted one"
"from the rust-colored estate"
"man of Rome"
"strength, powerful one"
Similar sound: These names share phonetic patterns with Astro — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Greek origins, giving them the same cultural heritage as Astro.
Rhythm: Astro is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.