I envy you!
Jeg har slektninger i Sverige!
I wish I'd have
person som en er i slekt med
is the "en" necessary here?
Yes. Note that it's a pronoun, not an indefinite article.
Is "slektninger" supposed to be pronounced with a "sh" sound?
Yes, look at the notes of the very first lesson. "Sl" produces a "sh" too
jeg ikke.. altfor dårlig
I actually do have relatives I talk to living in Norway! :)
I did have relatives in Norway, but I'm not sure if they're still around. I don't even know their names! I guess I should find out...
why doesn't "siblings " work in this sentence?
Because that is not the word stated in the Norwegian sentence. Despite the fact that siblings would indeed be your relatives, relatives aren't necessarily your siblings.
Conclusion: "slektninger" =/="søsken"