Sure, but (I know nothing about scandinavia, so I might be wrong), there are less differences trough Danes and Swedes than through Irish and British peoples, at the beginning of the time line (for example) ?
Depends on the 'British', Irish were very different to the Welsh, completely different to the English and low-land Scots but almost identical to the Highland Scots whose language was often called 'Irish' by English speaking Scotsmen (nowadays they are called 'Irish Gaelic' and 'Scottish Gaelic' and have diverged a bit more, but Irish, Gaelic and Scottish were all originally synonyms from different languages). Swedish and Danish were continuums, so Swedes in Finland would be quite different to Danes in Schlesvig, but Danes in Scania would be closer to Geatlanders across the border than to their countrymen in Schlesvig and Geatlanders would be closer to Scanians than to Norlanders and Swedish speaking Finns.
The Dutch and Germans are similar.