As a
Finn, I think that
Mikael, Helinä,
Elisabet and
Emilia could be an actual Finnish sibset.
Elisabet stands out a bit, though: it's normally used as a middle name, while
Liisa,
Elisa and
Elsa are more common as first names. If they're a Finnish-Swedish sibset, then Helinä is a bit weird: you could change it to
Helena. Also,
Emilia is a bit more modern than the other names: it's been quite popular from 1980's to the current day, while
Elisabet, Helinä and
Helena were more popular during the first half of the 20th century.
Mikael is pretty much like
Michael in the English-speaking countries, that is it has been very popular throughout the last century.
Caspar,
Olivia,
Lovisa or
Viola seems very believable to me, too. I'm not sure about the situation in Sweden, but at least in Finland
Viola has been slightly more common than
Lovisa (or
Loviisa) in recent years. Also,
Casper is more Swedish form, but
Caspar will do just fine.