I never know him, let alone his family.

我从不认识他，更别提他的家人了。

youdao

Never know him!

永远不会知道他！

youdao

There was still the faint hope deep within him that she might never need to know.

他内心深处仍然存一线希望，希望她会永远都不想知道。

《柯林斯英汉双解大词典》

"You would never know to look at him that he has spina bifida, " his mother said.

CNN: Study: Major benefits for spina bifida surgery in the womb

None of his players get a chance to overpower him you and never know if you're going to be in the team or not.

BBC: Everton ready to win Cup - Moyes

And they would never miss the chance to let him know that.

ECONOMIST: In search of the real Camus