Complex sentence: In 1756, Mary moved to Denmark, to take care of the children of her sister, Louise of Great Britain, who had died in 1751; her children was raised at the royal court and her sons married to Danish princesses.
Split into simpler sentences: In 1756, Mary moved to Denmark, to take care of the children of her sister, Louise of Great Britain, who had died in 1751. She took her children with her; they were raised at the royal court and her sons married to Danish princesses.