I am not licensed in OK. However, in general courts often look for the best interests of the child. Grandparents therefore potentially can figure into the situation.
This post is not legal advice, and does not create a lawyer-client relationship.
for the most part, the answer to your question can be found in the Oklahoma Statutes at Title 43, Section 109.4. You can find it on the web at: http://www.oscn.net/applications/oscn/DeliverDocument.asp?CiteID=63769
Hope this helps!