Linnea is my favourite girl name ever (if I'll ever get a daughter, I will most definitely call her
Linnea), and I love the name
Linus. The combos sound very nice, too - especially
Linus Gideon.
I'm not sure about wheter they sound too similar for a twin set. I'm personally not so keen on sib set starting with the same letter, but
Linnea and
Linus aren't that close because the names are not related (they're not exactly
Alexander and
Alexandra,
Simon and
Simone, or
Victor and
Victoria). Yeah, I guess it could work.