Need help or information on unsolicitedoil, gas, mineral and road use agreement received

I just received an Oil, Gas and Mineral Lease and Road Use Agreement for 40 acres l own in Beauregard Parish, LA for 3 years and other stipulations. The land is owned by several family members and we each got sent leases for the property. Can anyone tell me the going rate of leases for this area? Should I have a lawyer look the papers over? And, what happens if some family members sign and others do not?