adjective

lacking initiative or strength of character; irresponsible.

her feckless younger brother

useless,worthless,incompetent,inefficient,inept,good-for-nothing,ne’er-do-well,lazy,idle,slothful,indolent,shiftless,spiritless,apathetic,aimless,unambitious,unenterprising,no-good,no-account,lousy