And I restored the union, but a month later the union ended again when my ruler died??!!

https://eu4.paradoxwikis.com/Personal_union#Independence

If the senior partner's ruler dies while the junior partner has a negative opinion of its overlord, the junior partner will become an independent nation again and be assigned a new ruler of the same dynasty. The senior partner will get a "Restoration of Union" casus belli. A junior partner can also declare war on their senior partner at any time - even while the nations are in a war together - to gain their independence. If their liberty desire remains low, then they will never declare independence. Once the player has a high enough development and strong enough army versus their personal union subject, they will never declare independence on their own, even at high liberty desire.

Note that Disloyal attitude disloyal or Rebellious attitude rebellious subjects can accept support independence offers from other countries (typically the player's enemies), which will increase their liberty desire significantly and cause them to declare a war for their independence, where the goal is for the attacker to defend its capital.

ive experienced this too with sweden, while having great relations, below 50% liberty desire and no pretenders and also beeing at war.
i thougt at first i might have missed the rebels so i "alt + f4"d the game and reloaded but the same thing happend again.
iam not sure what the trigger is but i think there might be some kind of event on the swedish side.

Originally posted by ac_denton:

https://eu4.paradoxwikis.com/Personal_union#Independence

If the senior partner's ruler dies while the junior partner has a negative opinion of its overlord, the junior partner will become an independent nation again and be assigned a new ruler of the same dynasty. The senior partner will get a "Restoration of Union" casus belli. A junior partner can also declare war on their senior partner at any time - even while the nations are in a war together - to gain their independence. If their liberty desire remains low, then they will never declare independence. Once the player has a high enough development and strong enough army versus their personal union subject, they will never declare independence on their own, even at high liberty desire.

Note that Disloyal attitude disloyal or Rebellious attitude rebellious subjects can accept support independence offers from other countries (typically the player's enemies), which will increase their liberty desire significantly and cause them to declare a war for their independence, where the goal is for the attacker to defend its capital.

The problem is though they had 200+ relations and less than 50% liberty desire. The union just ended while my king was still alive.

I've seen that happen too. They just randomly end the personal union despite having good relations, low liberty desire, and a leader not dying either. There must be some event happening in Sweden.

Not just Sweden, just lost Italy as Agnevin Empire while +200 opinion and 0% disloyal

What is with all the necro threads the past couple days????

Originally posted by astrolamb:

Not just Sweden, just lost Italy as Agnevin Empire while +200 opinion and 0% disloyal

Also, so what? Maybe they had pretender rebels that you didn't notice because of inattention or bad message settings. If the pretenders win, you lose the union no matter what opinion or loyalty they have.

Originally posted by astrolamb:

Not just Sweden, just lost Italy as Agnevin Empire while +200 opinion and 0% disloyal

Whatever was the cause for the people in this thread has probably been long fixed and is not related for what happened in your case. Did you check if they have rebels or if they got an event? If you have a save in which this is about to happen, you could load it as Italy and see what is happening from their perspective