Is it common for kings to use their mother's house in titles?

Question

In season 1 episode 7, "You Win or You Die", of Game of Thrones, the scene where Ned tried to expose that Joffrey is Jamie's bastard, not trueborn of Robert, Joffrey is shown to be styled by the names of both houses, Baratheon and Lannister:

All hail his Grace, Joffrey of Houses Baratheon and Lannister, the first of his name, King of the Andals and the First Men, Lord of the Seven Kingdoms and Protector of the Realm.

Is it common for kings to be styled with their mother's house? Because to me, if it is not common practice, then this is not the correct time to do so. Especially when someone is trying to reveal that he is indeed a Lannister bastard and also it implies that the Lannisters are trying to capture the throne.

Answer 1

In universe: It is a fantasy show, not a show depicting a realistic medieval setting. It orients on the (mostly) European medieval times (the imagination of which that most people have is in itself largely an invention by novelists and romanticists), but huge parts are altered and sometimes not very believable, including measurements, distances, time spans, anachronisms, organisations, religions, marriage customs, heraldry, dragons, and zombies. I wouldn't expect a realistic depiction of certain name rules there. Whatever happens in Game Of Thrones is realistic in Game Of Thrones as long as it doesn't contradict any rules within the show. As no one of the characters took offence at it it seems to be acceptable within the setting.

Out of universe: Practically each country, each class, and each family had their own rules that were changed over time and to represent the current situation of power. Often the patrilinear descendency was relevant; sometimes the bearer of an office was the defining part. E.g. the next king of England will be from House Windsor (mother) instead of House Schleswig-Holstein-Sonderburg-Glücksburg (father).

In the show Cersei styles herself "queen" when taking regency, ignoring Robert's will. She, having the power, knowing the truth, despising her former husband, takes over. Weren't it for reasons of Robert's (weak) claim for the throne I bet she would have dropped the stag completely.

Answer 2

This is somewhat uncommon, especially to use the names of both the mother and father's house. However; my knowledge is mostly in England and the UK. I know that James I of England took his mother (Mary Queen of Scots) house name of Stuart, but his father was regent only and was a complete scoundrel. However, Mary Queen of Scots kept her house name of Stuart from her father, James V of Scotland.

Queen Victoria remained at the house of Hanover even though her husband, Prince Albert (who was regent only) kept his house name of Saxe Coburg-Gotha. Their son, King Edward VII, who succeeded the throne after Victoria's death took his father's house name instead of his mother's, who was actually the Queen.

William and Mary of the house of Orange, Queen Anne of the house of Hanover, Queen Mary I and Queen Elizabeth I both of the house of Tudor had no children to survive to adulthood. Queen Elizabeth II naturally assumed her Father (George VI) house of Windsor.

So, I am pretty sure that when Prince Charles succeeds to the throne that he will take the house of Windsor, which is his mother's, but it was first taken by his great-grandfather George V, so it is not like Elizabeth II created her own house. Here is a great website if you want to check my facts.