Ratchatrakul (ราชตระกูล) are the royal houses which are descended directly from the siblings of King Rama I. This refers to those not of the immediate royal family, meaning those of the rank of Serene Highness (Mom Chao) or below. Untitled ratchasakun or spouses of ratchasakun shall take the suffix of na Ayudhya (modern alternatives: Na Ayutthaya) behind the surname as well, to signify royal heritage.
