So I thought about it just now, and not sure if I'm going to write about it, but I might.
Assuming Luna is the illegitimate daughter of Nora and Miguel (whose eventually adopted by Linnie), I theorize that eventually, Miguel realizes that he does love the child, but by the time he realizes it, it's too late to get the child into custody. The only way Miguel could take Luna back is if Linnie was abusive (in which no way would he be. He loves her with all his heart). Plus, Miguel knows that Luna would have a better life if she stayed at Linnie's since she wouldn't be exposed to alcohol, and Linnie is a lot more patient when it comes to young children.
On knowing this, Linnie is kind enough to set up times where Miguel can visit Luna; both of them bonding and playing with her, Luna calling both Miguel and Linnie daddy. Miguel would also sometimes send Luna gifts, that help Linnie take care of her.
Meanwhile, Linnie absolutely does not want Nora interacting with her. Before her death, Linnie tries not to interact with her as much, as Nora never finds any interest in the child, and fully believes that the child should have never been born.
