I rather believe he is the natural son of some rich man.

我更相信他是某个有钱人的亲生儿子。

He was rumoured to be the natural son of a duke.

【natural，naturalness】谣传他是某位公爵的私生子。

Arabella's two children, who were amazingly like de Marsay (a natural son of the old lord), were near their mother; de Marsay himself was on the sofa beside her.

阿拉贝拉的两个孩子非常像德·马赛（老爵爷的亲生儿子），离他们的母亲很近。 de Marsay 本人坐在她旁边的沙发上。

" The natural son of the Emperor of Russia ... who would be made a sovereign in honour of his marriage, or quite simply the comte de Thaler, who looks like a dressed-up peasant" .

“俄罗斯皇帝的私生子… … 为了纪念他的婚姻，他将被封为君主，或者简单地说是德·塔勒伯爵，他看起来像一个打扮得漂漂亮亮的农民”。