The dual appointment was carried out because the Prefect of the Papal Household, must also be an archbishop. Up until now, Gaenswein had not held that rank.
Previously the Prefect of the Papal Household was James Harvey. In November he left that post, when the Pope made him a Cardinal and the archpriest of the Basilica of St. Paul Outside the Walls.
Gaenswein will probably be ordained a bishop by Benedict XVI on January 6th which is the same day that Nicaragua's nuncio Fortunatus Nwachukwu will be assigned. With Gaenswein's coming appointment, he will manage the Papal apartment along with Father Leonardo Sapienza, who serves as Regent of the Prefecture of the Papal Household.