Indeed, the further you go back in history, the more cases you'll find, with a greater likelihood of the specified scenario (the father of the king's bride being himself an enthroned king), since death rates were high. One did not have a situation like in Bernadotte Sweden, known for the longevity of their kings (Gustaf VI Adolf was a longtime king-in-waiting). Or Denmark, where King Frederik VIII was known as the "Eternal Crown Prince" because his father (King Christian IX) lived to the age of 88. Even though he married, in 1869, the daughter of an enthroned king (Princess Louise of Sweden was the only surviving child of Carl XV, who died three years later), that union obviously didn't count.

In the past, royal marriages not only were typically arranged but also, sometimes involved the betrothal of young children. I believe that was precisely the case with the English princess Eleanor (named after her mother, the famous Eleanor of Aquitaine), who in 1170 became the child bride of King Alfonso VIII of Castile (enthroned in 1158, not long after his father-in-law succeeded to the throne of England as King Henry II Plantagenet).