Regan sits next to 4 phonetic neighbors — Reagan, Keegan, and Brogan are the closest matches by sound. Most share Regan's Irish-rooted cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"little king, of royal descent"
"God will add, increase"
"king's town"
"dark one, black-haired"
"modern expansion of Azariah"
"descendant of Ógán"
"ash tree town, settlement near ash trees"
"the Lord is salvation"
"born at daylight"
"hunter"
"spring-like, of the spring"
"lord, chief, ruler"
"little Hugh, small-hearted one"
"God is gracious"
"my light, my flame"
"peaceful town"
"modern coined name"
"grace of God + home ruler"
"fashionable, sharp (modern connotation)"
"emperor, ruler, caesar"
Similar sound: These names share phonetic patterns with Regan — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Irish Gaelic origins, giving them the same cultural heritage as Regan.
Rhythm: Regan is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.