There's quite a bit of information on George Milford-Haven in Richard Hough's book "The Mountbattens", which I just finished re-reading. According to the book, the Mountbatten family divided themselves up two ways by personality- Victoria, Louise, and "Dickie", (the younger Louis) being the extroverts, and Louis, Alice, and George being quieter. George was very intelligent, according to Hough "he read books on higher calculus casually in trains, or in the evening with people talking all around him". I imagine he had to learn to read while people were talking with a mother like VMH! He reached the rank of Commander in the Royal Navy, and "He was a born leader,like his father, and possessed enormous charm. The men loved him, and unlike his father and his younger brother, who had their difficulties, he got on immediately and very well with his fellow officers and superiors." He served in the Navy during WWI. He retired in 1932, and worked for the British Sperry Gyroscope Company.
There's not much on his wife in the book, unfortunately. Hough does say that when George and his younger brother were both serving in the Mediterranean Edwina and Nadejda shared Casa Medina, a villa rented in Malta, where it seems VMH would visit them. From photographs Nadejda looks beautiful, I wonder if there are any portraits of her out there?