Sawtooth Spire You took my hand and we pretended like I was your guy

Thade, too, to say nothing of the forlorn Astraeus. Wylla didn't look at him like a son—he was merely an orphan she fed and kept warm so he would live, to strengthen and diversify Sagtannet with young blood other than Mahler's—but she hadn't overlooked Mahler's more fond interactions with the boy. He was already a sullen thing, and she loathed to think how bothersome he'd become when Mahler was away with Nyx. On the subject of Thade, she couldn't guess at a reaction.
Jealousy curdled in the pit of her stomach, made little better by Mahler's logic.
It was a cold sort of logic, no doubt meant to appeal to her sensibilities, as her heart was firmly locked behind her notion of injustice. It didn't have that effect, although it didn't quite have the opposite effect, either. It didn't make her angrier to think she needed to swear herself to Mahler in order to stick it to Nyx—she didn't care enough about her brothers' former friend to think that—because even doing so would not dampen the effort he made for his children with Nyx, nor elevate the effort he made for hers above the effort he made for them.
That was Mahler's greatest strength and greatest flaw both, in Wylla's eyes: he saw equality where she didn't believe there was any. He would adopt every child upon the mountain if he could, treat them as his very own, whereas for Wylla, the blood family was the most important of all, and she could never manage to treat non-blood the same as blood.
You're asking me to commit myself to a man who hasn't yet fully committed himself to me, Wylla remarked. He should consider her offer to legitimize her children—that was the gist of what he'd said. Not for lifelong commitment to one another, but for legitimacy and the right of a title over the other children he'd sired. That wasn't enough for her. I cannot hitch my life to yours until I see for myself that what you're upholding with her is really just a contract, and not some kind of emotional affair.
She would not be brought into a relationship with someone who loved another, and she was too paranoid to take his word for it with children on the line. It wasn't that she wanted him to abandon Nyx's pups. She would never see them as equal to her own or worthy of his equal attention, but they were kids and they didn't deserve abandonment. She just wasn't ready to trust that Mahler's choices were based in logic and not in lust and repressed feelings.