If I'm reading you right, the person who changed their plans, is involved, but may not know that they were involved. I'm thinking along those lines on someone too.
I don't think, though, that this is about custody, in the traditional sense. I haven't seen the two parents fighting online, or any court proceedings, over custody of the child. Also, JW had irregular hours, as an OTR trucker. He gave that job up, after HMR's murder, not before, to be closer to S. Nothing against him having the previous job, it just seems that he was fine with things, the way they were, and said as much. He was doing what some parents
never do. He worked, and made time for his daughter.
After the murders, he even took S to see her great-grandmother, GR, and said he hoped that S could stay in contact with her sister, if he was not the infant's father.
If this was about custody, solely or in part, I don't think it was over time allocation with the child, not paying support payments, or who wants primary custody. I think this was about hate, and/or revenge. Someone hated these folks bad enough to want them dead. If it was about the child, they wanted to make sure that those eight people were never, ever, able to be a part of the child's life again, and there was only one way for that to happen.
http://www.cincinnati.com/story/news/2016/07/29/rhoden-case-hate-seeing-my-daughter-cry/87645382/