In my opinion, this is why you need both parents to be capable. Even the late LKY agrees with me. in Lee Kuan Yew: Hard Truths to Keep Singapore Going, he argues that IQ is inherited. In fact, he said: “So when the graduate man does not want to marry a graduate woman, I tell him he’s a fool—stupid. You marry a non-graduate, such as your personal assistant or subordinate, you’re going to have problems: some children bright, some not bright. You’ll be tearing your hair out.”
Although there may be occasional cases of high-IQ parents having low-IQ children, the numbers are not substantial enough to warrant concern.