fill combobox with data from another combobox

I have a City table where you have the fields NameChild, IdEst, IdPais, in addition to the State and Parent tables. I'm doing an application in C # where I use 3 combobox. When selecting the first combobox (cboCity) and choosing a record, I want the same states and countries of the combobox cboEstado and CboPais to be selected at the same time. Remember that the combobox State and Country are already filled with their respective values of the tables (State and Country)