The royal House of Sia originated from the planet, Naboo.
Origins
Centuries ago, when Naboo was still in a period of a true Royal blood Monarchy, before the elections were put into place, House of Sia existed as one of the few royal houses active on the system at the time. When King Veruna died, (the last true royal monarch of Naboo) he failed to leave an heir behind. This then lead into a great political war. Royal houses were fighting one another for claim to the throne whilst the people of Naboo were scared of another possible tyrant like King Veruna. This lead to a neglect of other Royal Houses such as House of Sia and paved the way for elected monarchs to take charge, hence Queen Amidala was voted into office by decree of the council and of the people. Ruining any chance of other royal houses claiming the throne for themselves.
During Queen Kylanthas reign ((a canon queen, much like king Veruna was a canon king)), she dropped the two terms that an elected Monarch could serve, shifting Naboo back into a true Royal Monarchy state. The first period of a true royal blood monarchy since King Veruna died. After Queen Kylanthas death a relative inherited the throne and so forth the Monarchy grew once again.
Because of this, the Royal House of Sia has BOTH the legitimacy and now the possibility of claiming the throne for themselves.
Claims in Onderon
Sometime after the people of Naboo chose to neglect the royal houses of Naboo in favour of an elected monarchy, House of Sia got clever and married their descendants to that of Onderons own royalty. From these marriages, their children were both legitimately royal in Onderon as well as Naboo (after Queen Kylantha dropped the elections). This is further supported and actually confirmed by the fact that Amidala Sia herself was part of the line of succession for the Onderon throne when her AUNT, Queen Astra, who succeeded Queen Hyacinth asked her to join her in the Onderon Royal court. This also confirms that through blood, both Queen Hyacinth and Queen Astra who are both famous Queens of Onderon, were also members of House Sia themselves whether they knew it or not. This means that House of Sia also has legitimate claim to Onderon.
Line of Succession:
- Queen Kida Sia (Current Monarch of the Sia Dynasty)
- Janelia Sia (1st in line. Crown Princess)
- Pindara Sia (2nd in line)
- Felina Sia (3rd in line)
- Amidala Sia (4th in line, deceased)
- Queen Astra (5th in line, deceased)
- Calliope Quan (6th in line, deceased)
- Orion Janick (7th in line)
- Thalia Ishtari (8th in line)
- Tiffany Vandergraff (9th in line)
- Hyacinth Janick (10th in line)