Monarchys in General

This is just a what if question,but lets say the Swedish king has only two children one of them is a female and she gets married to the hier to the throne of Norway his son dies childless and his daughter has but one son would he become king of Sweden and Norway i mean in the 21 century i know this has happen befour but today people tend not to take kindly to foriegn rulers.

I'm going to try to understand what you were asking:

King of Sweden has 2 children, 1 boy, 1 girl.
Girl marries Crown Prince of Norway and they have one child, a son.
Swedish Boy dies without an heir. Would the sister's son be king to both the Norwegian and Swedish thrones?

Am I correct in my interpretation?

Ok, I'm going to state right away that I am venturing my guess... it's most likely not correct... but hey, I want to answer, so here I go:

In the Swedish Act of Succession, Article 8, it says that "A prince or princess of the Swedish Royal House may not become the sovereign ruler of a foreign state whether by election, succession, or marriage without the consent of The King and the Riksdag. Should this occur, neither he nor she nor their descendants shall be entitled to succeed to the throne of Sweden."
http://www.riksdagen.se/english/work/fundamental/succession.asp

In Article 10 of the Norwegian Constitution, is says, "The King shall reside in the Realm and may not, without the consent of the Storting, remain outside the Realm for more than six months at a time, otherwise he shall have forfeited, for his person, the right to the Crown.

The King may not accept any other crown or government without the consent of the Storting, for which two thirds of the votes are required. "
http://odin.dep.no/odin/engelsk/norway/system/032005-990424/index-dok000-b-n-a.html

So in a few words, I'll say it's highly unlikely. The daughter who married the Norwegian Crown Prince would be in line before her son, unless she signed away her succession rights at the time of her marriage, which would be more likely. That would mean her son is ineligible for the throne of Sweden also. But I will say that a King/Queen who has no children usually has an heir lined up in the event of their death... a brother, sister, or other eligible family members. Like Nicholas II's named heir was his brother George (until his death in 1899) and then brother Micheal (until Alexei's birth in 1904). But anyway, since his sister was his heir, it would be also unlikely that she would have been allowed to marry the Crown Prince of Norway until her brother had legitimate children of his own.

Does this make any sense?  

Nerdycool has got it right in just about every respect.
The constitution of Norway says that no royal prince of the Norwegian royal house may accept another crown without the consent by two thirds vote of the Storting.
It is unlikely that such a majority could ever be achieved. Personal union of crowns has a rather disastrous history in Norway.
Most likely the next King (Queen) of Sweden would be one of the brother's uncles, aunts or cousins according to the legitmate line of succession.
The son of the sister could abdicate his rights to the crown of Norway and become the Swedish king, but that is unlikely.
Each country with a monarchy  has different laws on the succession. One good website to go to for a lot of links on royalty and questions of royalty is Hoelseth's Royal Corner.
www.geocities.com/dagtho/royalty

Here is an example of a convoluted line of succession:
The Grand Duchy of Saxe-Coburg and Gotha was ruled for most of the 19th century by
1. Grand Duke Ernst II--brother of Albert, Prince Consort and husband of Queen Victoria.
2. He died without heirs in 1893 and so his successor was his brother Albert, but he was dead(1861).
3. Victoria and Albert's oldest son was Edward, Prince of Wales (Later King Edward VII). He was the next legitimate successor to the Grand Duchy. But the throne of England was a much better prize, so Edward abidcated in favor of his brother, Alfred, Duke of Edinburgh (not the present one).
4. Alfred ruled as Grand Duke until 1900 when died of throat cancer. He had only one son, also Alfred (Little Alfie) but this son had died before Alfred (1899).
5. Therefore, the throne passed to Edward and Alfred's younger brother, Leopold, Duke of Albany.  But Leopold had haemophilia and had died in 1887. Therefore,
6. His son, who had been born after his father's death (his mother was pregnant with him when Leopold died),
Charles Edward, Duke of Albany, succeeded and became Grand Duke of Saxe-Coburg and Gotha.
He reigned until the end of World War I when Germany became a republic and these small kingdoms and grand duchies were done away with.
7. Charles Edward had several sons and their descendants are the present claimants to the throne of the Grand Duchy.
There is always a successor somewhere, no matter how far away in relationship to  the reigning sovereign. The King is dead! Long Live the King (or Queen)!

Here is an example of a convoluted line of succession:
The Grand Duchy of Saxe-Coburg and Gotha was ruled for most of the 19th century by
1. Grand Duke Ernst II--brother of Albert, Prince Consort and husband of Queen Victoria.
2. He died without heirs in 1893 and so his successor was his brother Albert, but he was dead(1861).
3. Victoria and Albert's oldest son was Edward, Prince of Wales (Later King Edward VII). He was the next legitimate successor to the Grand Duchy. But the throne of England was a much better prize, so Edward abidcated in favor of his brother, Alfred, Duke of Edinburgh (not the present one).
4. Alfred ruled as Grand Duke until 1900 when died of throat cancer. He had only one son, also Alfred (Little Alfie) but this son had died before Alfred (1899).
5. Therefore, the throne passed to Edward and Alfred's younger brother, Leopold, Duke of Albany.  But Leopold had haemophilia and had died in 1887. Therefore,
6. His son, who had been born after his father's death (his mother was pregnant with him when Leopold died),
Charles Edward, Duke of Albany, succeeded and became Grand Duke of Saxe-Coburg and Gotha.
He reigned until the end of World War I when Germany became a republic and these small kingdoms and grand duchies were done away with.
7. Charles Edward had several sons and their descendants are the present claimants to the throne of the Grand Duchy.
There is always a successor somewhere, no matter how far away in relationship to  the reigning sovereign. The King is dead! Long Live the King (or Queen)!

Edward VII was never, in fact, the next legitimate successor to his uncle's grand ducal throne, due to Saxe-Coburg household laws.  His brother Alfred had been designated Ernst's successor in 1842, before Ernst himself even acceded!  After Alfred became Duke, his son of course became the Hereditary Prince.  When he died, the Connaught line (Arthur and his son) were next in the line of succession, but the Connaughts declined, and that left Leopold's surviving son, Charles Edward, who was pretty much forced to accept, and was uprooted and sent to Germany as a teenager.

Convoluted, indeed! :)

Did Vicky (Empress Frederich) spend a great deal of time with the Saxe Coburgs and in their homes/castles, given that these were the relatives of her dear father?

She must have visited quite a bit, or they visited her.  And not just the S-C-Gs. She seemed to know what was going on in every family on the Continent ! And this in the days before email !!

Point of clarification....the Saxe Coburg Gotha duchy was its full name, right? QV, from Albert, used the family name Saxe Coburg Gotha, right? Yet, some refer to the family name as simply the Coburgs? How do all three names interplay? Thanks,.

Sachsen-Coburg-Gotha.

Is it Koburg or Coburg?

She must have visited quite a bit, or they visited her.  And not just the S-C-Gs. She seemed to know what was going on in every family on the Continent ! And this in the days before email !!

I think women went to her for advice.  I know I would have look her up in I needed or wanted an opinon on something.

TampaBay

Really ? I would have stayed as far away as possible from the old busybody ! [but I know she still would have found out what I was up to]

Really ? I would have stayed as far away as possible from the old busybody ! [but I know she still would have found out what I was up to]

She wasn't an old busybody...she was wonderful. I'd have gone to her too for any kind of advice!

Well, I consider her a busybody.Obviously you do not. I would have packed my bags if I knew she was on the way !

You'd have fared much worse if her mother had come to visit...now she WAS a busybody (& a very interesting one too!)