When Nightfall visits, Yor expresses self-doubt about how much she can actually help Loid and contribute to the family - as she says, she is lacking.
What she forgets though, is the 'half a wedding vow' that Twilight gives her when he first asks him to be a partner in parenting Anya: Yor will be everything he lacks, she will be everything he's not. But what's unspoken is that this relationship is reciprocal - he will be what she lacks, he will be what she's not.
And she is. Yor provides Anya with all the physical affection Twilight is not ready to show his daughter just yet.
She cares for Anya when he's not around.
She plays with Anya when he can't.
She is slowly making him understand he had worth as a man, not the Spy, that he should look after himself.
She is his rock, his strength, bringing him down to earth, reminding him he is only human when his Spy Brain kicks in and he blames himself for not being perfect.
Sure, Yor might be lacking in some areas. But her flaws have never troubled Twilight. Even at the start, when his wife was truly 'pretend', he understands everyone has their strengths and weaknesses. And he eats all the food she lovingly serves him, never complaining.
Because he is what she lacks, what she is not. He is her confidence. He assures her she is a good mother. He makes her come out of her shell. He makes her smile.
Yes, in a sense, both Yor and Twilight are lacking. But their strengths and weaknesses complement each other. They support each other, they work as a team, they are partners, whether they know it or not.
But neither of them actually lack anything, because they have each other. 🥲