Houston Private Investigator for Real Estate

Currently working with a Real Estate Lawyer to clear title issues on my grandmother’s house. I need to find 3 family members that up to 4 weeks ago we didn’t even know we had. Lawyer advised that i would need a private investigator to do this, anyone here know of any Private Investigators that either specialize or have worked with these types of situations? Also for anyone here that has been in this situation, how much should i expect to pay for this type of work (need to find 3 people)