in short, 弟 is fraternal; translated as "a good citizen" is, imo, incorrect.
in long, i would inteprete the sentence:
as a human being (其為人也), someone (者) who is filial (孝), fraternal (弟), and (而) prefer (好) against authority (犯上), it's rare (鮮矣).
that, 孝 (filial), is 善事父母 (performing one's duty as a son), while 弟 (fraternal) is 善事兄長 (performing one's duty as a younger sibling; and to perform well.
therefore, a children would internalise a submissive attitude, which would be obedient toward parents, older siblings in family; afterward, they would conform to the authorities in society.
that's the norm of confucian.