There is something no one is saying.
What if it's a girl?
Robert can't help but think of his legacy, his home, his wife's fortune, all inextricably tied to the gender of his child.
A boy would be the answer to his prayers, but Robert knows all too well the danger of unrealistic expectation. He has first-hand knowledge of the injustice of placing the precarious and precious future of Downton on one person.
That night, when he feels his child bump against his hand for the first time, he touches his future and his true legacy.
No matter what.