I was thinking this morning:
If the McClarans were in a dispute with anyone, all records of communication (on the McClarans end) with the person would've been destroyed in the fire. I hope family members and close friends of the couple have been questioned thoroughly as to any knowledge of a dispute.
If there was a dispute over the custody of the children and the object of the perp was to claim the children, there was likely no legal record of a custody battle since the McClarans were not the legal guardians. Do family members know of any other family members who objected to the McClarans having the children?
There could also have been a non-custody dispute between the McClarans and someone else. It could have been over money, land, any number of things. If the object of a perp was to kill the McClarans and cover up the murder via arson, the person may have had sympathy toward the children and spared their lives. But, knowing that the children are witnesses, the perp would keep them hidden away.
If a crime has occurred ... i.e., a murder, arson and abduction ... it is more likely that it was committed by someone known to the family, and this is a more hopeful scenario than a random targeting. While several family members have spoken with LE and some publicly, albeit briefly, if family and friends have suspicions about anyone, it is not something they would want to divulge publicly. There really isn't that much they can say until LE determines how the McClarans died and how the fire was started.
Until it is declared a murder, arson and kidnapping, family members can only speculate, and if a crime has truly been committed, speaking prematurely may only spook the perp to go deeper into hiding and the children will more difficult to locate. With this is mind, I think LE believes that a crime has been committed and someone known to the family is responsible.