I love [name]Axel[/name], very scandinavian. Have you looked through lists of other scandinavian names to see if there are any you like? I suggest using behindthename.com, they have a whole list of Scandinavian names to choose from, if you like those type of names.
Also, I think [name]Ingrid[/name] is the perfect sister name for [name]Axel[/name]! They complement one another very well.
As far as brothers go off the Scandinavian list, I like:
[name]Andreas[/name]
[name]Anton[/name]
[name]Casper[/name]
[name]Elias[/name]
[name]Felix[/name]
[name]Finn[/name]
[name]Gabriel[/name]
[name]Greger[/name]
Henrick
[name]Hugo[/name]
[name]Isaac[/name]
[name]Jonas[/name]
[name]Kai[/name]
[name]Konrad[/name]
[name]Linus[/name]
[name]Lukas[/name]
[name]Magnus[/name]
[name]Markus[/name]
[name]Marius[/name]
[name]Mattias[/name] or [name]Mathias[/name]
[name]Morten[/name]
[name]Maximilian[/name]
[name]Olav[/name]
[name]Oliver[/name]
[name]Oscar[/name]
Ragner
[name]Reuben[/name]
[name]Solomon[/name]
[name]Sebastian[/name]
[name]Sander[/name]
[name]Simon[/name]
[name]Soren[/name]
[name]Stellan[/name]
[name]Theodor[/name]
[name]Thorsten[/name]
[name]Tobias[/name]
Torben
[name]Viggo[/name]
[name]Victor[/name]
[name]Vincent[/name]
[name]Do[/name] you like any of those or am I on the complete wrong page?