As far as I can see,
Prince Ferdinand Philippe, Duke of Orléans, the oldest son of King Louis-Philippe of France, was a liberal, middle-class type of royal with a great deal of popular support. However, he died in an accident in 1842 at the age of 32. Six years later his father was forced from the French throne in the
1848 revolution, leading to the Second Republic, Second Empire, Napoleon III and so on.
However, what if he had avoided the accident that killed him?
Could the July Monarchy have come through the 1848 revolution intact, perhaps with King Louis-Philippe abdicating in favour of his son? From what I can see Ferdinand Philippe was popular, intelligent, had a sucessful military career, devoted himself to the military expansion and the improvement of the troops' living conditions and morale and was a great patron of the arts. If he had survived what could he have done for France? Where might it have gone from 1842 on?
And how long might the House of Orleans continue to hold the throne of France? Ferdinand Philippe had fathered two sons by 1840 and if he had not died he might well have fathered more children. Could France have carried on as a constitutional monarchy under them to the present day?