** SPOILERS **
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Lucia discovers she is pregnant in chapter 114 part 2.
And Hugh finds out that Lucia is pregnant, it’s in chapter 115 part 1.

Philip did, especially during war. If I’m not mistaken, during the war he prepared women (orphans and purchased slaves, virgins) to be sent to the duke without his knowledge. But women do not get pregnant because the Duke changed partners very quickly, and it is necessary for him to have a longer lasting contact for the pregnant woman.

And when women didn’t get pregnant, Philips killed them. And he failed to do that, because Hugh began to sleep with nobles and no longer with slaves or servants or something like that.

And since manipulating a noblewoman was far more difficult than slaves and orphans, Philip “gave up” on sending women to the duke. Or rather, he couldn’t do it anymore.