Literary and fairly bookish — closer to English 'chip off the old block', but more formal. 肖 here means 'to resemble', not 'Xiao' the surname, so it is read xiào (4th tone) — NOT xiāo.
mistakes
Do not confuse with 孝子 (xiàozǐ) 'filial son'. Both are pronounced xiàozǐ, but 肖子 is about resemblance while 孝子 is about filial piety.