He wouldn't do that. The child would obviously not be his (too dark) and he'd be a bit of a laughing stock.
They didn;t have sex anyway. Also it is obvious that he is attracted to her, even if he doesn't know it yet. He was very put out by, and was trying to follow, her conversation with the Turk at dinner. I can see why Mary is a fasicination to him. She is a cold hard character but if she thawed a bit she'd be alright I think and she is obviously very intelligent and a challenge.To a bloke like him, who is likewise (intelligent), it's an attraction.