as it should be by rights (idiom); proper and to be expected as a matter of course
inevitable and right
Definitions (粵典–words.hk)
形容詞
聽落去好合理、自然,冇咩好質疑 as it should be; assumed as reasonable, natural or true; expected as a matter of course; to take something for granted; of course; naturally
孝順父母都好理所當然。
孝顺父母都好理所当然。
haau3 seon6 fu6 mou5 dou1 hou2 lei5 so2 dong1 jin4. (One should) love their parents as a matter of course.
Definitions (Wiktionary)
phrase, idiomatic
to be only right and proper; to be taken as a matter of course; naturally (syn.) 应该然, 應該然, 當其然, 当其然