This manga isn't about the old guy finally getting back together with his dead wife, and starting the family over again, or whatever. It's about moving on after a SO has passed away.
For the most part it seems like the daughter has moved on. I'm sure she enjoys the company of her mother, but she seems to be fixing herself back into a proper member of society on her own.
The father, on the other hand, is too obsessive. He doesn't seem to want to grasp the fact that his wife isn't technically his anymore. He has this sort of tunnel vision where all he sees is bringing back something that can't exist anymore. He is going to get a heavy and hard slap in the face eventually.
I do lay some blame on the mother, however. She knows she needs to live a new life with her new family, but she keeps giving into her husband's demands. She either doesn't realize that she is hurting him in the long run or she is more worried about what will happen to him without her. Either way, with her around the father isn't going to make any progress with getting over her death. She's just going to push his assistant onto him and go back to her new family.