What number should replace the X to the magic square?

"Tony! Why are you so fat?"

"Pop, it's Mama's casseroles!" Tony says.

"I can't stop eating them, it's so good."

"Tony, you should take a smaller bites."

Pop says.

Then Pop looks at his middle son.

"Fred! Why are you so fat?"

"Pop, it's a Mama's roast beef," Vinny says.

"I can't stop eating it, it's so good."

"Fred, you should take a smaller bites."

Then Pop looks at his youngest son, "John! How you stay so slim and trim?"

"It's easy, Pop," John says.

"I eat a lots and lots of pussy."

"Pussy? Pussy?"

Pop says.

"That tastes like shit!"

"Pop, you should a take smaller bites."