Wes hal Castilius!

There is no doubt that the Germanic languages are IE. However, all the European IE languages show some oddities. Celtic and to a lesser degree Latin seems to have a Basque substrate (to be expected I supppose). Greek has substrata from several langauges. Then there are oddities within the IE family its self. From my readings I understand that the Germanic languages have a shared vocabulary with Celtic, Italic, Hellenic and to a lesser degree Baltic and Slavic. The other IE languages do not share this vocabulary apparently. The split is not quite the same as the Centum/Satem split. There are other oddities with Germanic that make some scholars think it is more closely related to Latin that any other IE language group, while others seem to think Baltic is the closest. In other words, the Germanic language group may be different simply due to encounters with other IE language groups before finally absorbing a non-IE speaking people. This is essentially what I think happened myself. Of course there is no way any of us will ever know I suppose.