I could only think of this one: https://www.novelupdates.com/series/the-end-of-the-worlds-poisonous-mom-and-monster-baby/ Child of female mc that doesn't make relation to ml And there's also this One Child Two Treasures: The Billionaire Chief’s Good Wife Or how about this one? Sons, Too Mensao- the sons became mls
There's one I remember.. ` Wicked Soldier King Spoiler: not really a spoiler but she ran away right after her marriage and that child is adopted
Kumo Desu ga, Nani ka? I'm just kidding. Though the main character Is badass and becomes (kinda) a mother. ...though there's no romance. Though there is a manga called 'Wicked Young Master's Forceful Love: Training the Runaway Wife' that might meet your preferences truly.
There's a wattpad story called Pick The Second Male Lead where it's more of a quick transmigration but there are arcs of badass divorcee with a cute child.