Back then, the Henderson family and the Miller family were family friends. Gabriela and Dylan were childhood sweethearts, so she more or less knew the inside story of the Miller family.
Most of the story was told to her by her father and Dylan.
Although Dylan and David were siblings, David was an in vitro fertilization baby specially hand-picked by the Miller family to assist Dylan.
After the death of Dylan's father in a car accident, Layton felt that the Miller family lacked manpower, so he used the frozen sperm that Dylan's father had preserved before his death to nurture a new member of the Miller family.
Therefore, David didn't have a mother. His position in the Miller family was awkward. He was like a descendent of the Miller family, but also like a servant.
Layton's feelings for Dylan and David were different. One was his grandson, and the other was just a servant, so even his expectations towards the two were completely different!