Discussing the possibility of some relative killing 8 Rhoden family members, let's take a look at Ohio law regarding people dying intestate (with no will):
http://codes.ohio.gov/orc/2105
Here are the pertinent parts of the law as they apply to the deceased Rhoden family members:
IANAL, but it looks like things go this way, WRT personal or real property or inheritance, after payment of taxes and debts:
CR1 - Personal and real property would pass to his surviving grandchildren
DR - Property would pass to her surviving grandchildren
FR - Property would pass to his surviving children
HG - Property would pass to her surviving children
HR - Property would pass to her surviving children
CR2 - Property would pass to his surviving grandparents
KR - Property would pass to his daughter
GR - If he has surviving children, property would pass to them. If not, it would pass to his surviving parents
Also, keep in mind that any debts owed by the deceased must be paid from their estate. In the case of CR1, if he had an outstanding balance on the bank loan acquired to purchase DR's home, the bank can ask that it be repaid from his estate. They also may choose to repossess the remaining property at DR's address. Other debts to be paid include taxes, credit card debt, any other bank loans, etc.
It's possible that other distant relatives, etc. of KR are filing claims on his estate because they claim he owed them money or feel they had some other legal claim. They would have to prove it in court and, outside of debts or partnerships, there aren't many other options.
If someone other than the victims took out AD&D insurance policies on them, it will be difficult to collect due to the suspicious nature of their deaths. The insurance company who sold the policy will likely withhold payment until the killers have been identified by LE. Any policyholder will have a difficult time collecting on those policies and will likely have to spend money on attorney fees.
Overall, I don't see any motive for the heirs of the Rhoden family to kill them. By the time taxes, debts and legal fees are paid, there probably isn't much cash left. Most of the real property is jointly owned with CR1 & KR's siblings. Any legal guardian of the grandchildren would have to get them to agree to sell the real estate or purchase their share in order to cash out. Since the heirs are all minor children, I assume a parent or legal guardian would have to get consent from the court to sell the inherited real estate.
LE and the courts have obviously been watching the guardianship and custody process for the minor heirs very closely and will continue to do so.