My previous game as Sigurdr went to hell for gavelkind-related reasons, but through careful planning I just did this:
As soon as the game started, I made Sigurdr divorce his wife, to prevent the birth of heirs other than Knud among which the realm could've been partitioned and, without selecting any ambition, I waged a war of conquest against the Swedish tribal realm; only then I selected the ambition to become king of Denmark, and annexed Jutland; the following war against the powerful Haraldr Fairhair was the last obstacle between Sigurdr and the direct or indirect rule over the whole of the Norse homeland: as soon as the Kingdom of Denmark was created, in 871, I made several tribal leaders swear loyalty to Sigurdr just by asking them, while the ones that were already my vassals were single-handedly responsible for plenty of conquests in northern Germany and the North Sea - only the Jarl of West Gotland, that had carved a realm for himself between Norway and Sweden, resisted the son of Ragnarr Lothbrok, something he paid for in blood.
I centralized the realm and improved the capital's infrastructure by spending on it almost all the money I had, so that when the Fylkirate was created in 885 I could transition to elective monarchy and feudalism - I didn't have enough Legalism for primogeniture. With succession secured, both Knud and Sigurdr married: Knud wed a Bohemian woman with the Genius trait that didn't pass on said trait to her children - she did however convert to the Reformed Germanic faith - while Sigurdr married an Estonian priestess he would soon enough proceed to cheat on with several women.
The Empire of Scandinavia was created in 908; at the ripe old age of 68, Sigurdr will probably die soon, having spent the last decade of his life involved in several wars.
The members of House Knytling in 908:
Fylkir Sigurdr, Emperor of Scandinavia, King of Denmark, King of Sapmi (68)
His children:
Prince Knud, Count of Vestergautland, son of Blaeja and heir to the realm (51)
Princess Skuld, Khatun of Bulanid and Shieldmaiden, daughter of Ere (19)
Princess Astrid, married to High Chief Yemelyan of Kiev and Shieldmaiden, daughter of Ere (18)
Princess Sigrid, daughter of Ulfhildr (12)
Prince Barid, son of Yngvild, a distant relative of Haraldr Fairhair (9)
Princess Yngvild, daughter of Yngvild (6)
Prince Tjudmund, son of Yngvild (1)
Knud's children:
Aslaug, married to Chief Einarr of Öland (16)
Sigurdr, bethothed to Elin, a direct descendant of Björn Ironside (14)
Hrolfr, a newborn baby (0)
As you can see, Sigurdr has a very active sex life for a 68 year old, and I forgot that you can't manage your children and grandchildren's marriages if you give land to them so Knud has made some very questionable choices that might come back to bite me in the arse later, but at least Sigurdr junior is not a younger version of Hodor like his older sister, he's just mediocre so far.