FULL PRODUCT VERSION :
MacBook-Pro-de-Alexander-2:staging alexanderdealmeidapinto$ java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Darwin MacBook-Pro-de-Alexander-2.local 16.3.0 Darwin Kernel Version 16.3.0: Thu Nov 17 20:23:58 PST 2016; root:xnu-3789.31.2~1/RELEASE_X86_64 x86_64

A DESCRIPTION OF THE PROBLEM :
When rowspan is used in a GridPane the correspondent cell dont have the expected behavior.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Execute the code bellow to note the problem.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
First row with double the height of the rest.
ACTUAL -
First row with minimum width and height.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.Priority;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class RowSpanExample extends Application {

public static void main(String[] args) {
Application.launch(SampleApplication.class, args);
}

@Override
public void start(Stage pStage) throws Exception {

final GridPane root = new GridPane();

final Region r1 = new Region();
r1.setBackground(new Background(new BackgroundFill(Color.web("#ff0000"), CornerRadii.EMPTY, Insets.EMPTY)));
r1.setMaxWidth(Double.MAX_VALUE);
root.add(r1, 0, 0, 2, 2);
r1.setMinSize(10, 10);

final Region r2 = new Region();
r2.setBackground(new Background(new BackgroundFill(Color.web("#00ff00"), CornerRadii.EMPTY, Insets.EMPTY)));
root.add(r2, 0, 3, 1, 1);

final Region r3 = new Region();
r3.setBackground(new Background(new BackgroundFill(Color.web("#0000ff"), CornerRadii.EMPTY, Insets.EMPTY)));
root.add(r3, 1, 3, 1, 1);

GridPane.setHgrow(r1, Priority.ALWAYS);
GridPane.setVgrow(r1, Priority.ALWAYS);

GridPane.setHgrow(r2, Priority.ALWAYS);
GridPane.setVgrow(r2, Priority.ALWAYS);

GridPane.setHgrow(r3, Priority.ALWAYS);
GridPane.setVgrow(r3, Priority.ALWAYS);

final Scene scene = new Scene(root, 700, 700);

pStage.setTitle("RowSpan Example");
pStage.setScene(scene);
pStage.show();

}

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :

//Add constraint for each row and column.

root.getRowConstraints().clear();
root.getColumnConstraints().clear();

final RowConstraints rowConstraint = new RowConstraints();
rowConstraint.setVgrow(Priority.ALWAYS);

final ColumnConstraints colConstraint = new ColumnConstraints();
colConstraint.setHgrow(Priority.ALWAYS);

for (int row = 0; row < mMaxRow; row++) {
root.getRowConstraints().add(rowConstraint);
}

for (int col = 0; col < mMaxColumn; col++) {
root.getColumnConstraints().add(colConstraint);
}