My wife and I are 70 years old, lives in Stockholm and has no children. There is no prenuptial agreement.
I have a brother that lives in Greece, a sister in Sweden and a deceased brother.
All have children. My wife is born in Poland, but has Swedish citizenship since 30 years.
My wife had two sisters who died, and she has nieces and nephews. We have a condominium in Stockholm, and a summer home in Poland.
Who inherits if I die, who will inherit if my wife dies and who inherits if we both die at the same time?
You have residence in Sweden and then the Swedish legislation.
According to Swedish law, inherits you as spouses to each other.
When you both have passed away, to share the estate, under the general rule, so that half is considered to come from you and the property of your relatives such as your brother, sister and the deceased brother's place to his children.
The other half is considered to come from your wife, and her property accruing under the law of her relatives, which seems to be her nieces and nephews.
If you don't want it, you must write a will.