Most linguists formally classify English as Germanic (West Germanic, alongside Frisian, Dutch and German, though one Norwegian linguist made a case for it being North Germanic), though some people refer to it as a Romance-Germanic creole. It is quantifiably true that, if you want to read Old English, knowing Icelandic will be more helpful than knowing modern English.
Most linguists formally classify English as Germanic (West Germanic, alongside Frisian, Dutch and German, though one Norwegian linguist made a case for it being North Germanic), though some people refer to it as a Romance-Germanic creole. It is quantifiably true that, if you want to read Old English, knowing Icelandic will be more helpful than knowing modern English.
And that as a native English speaker, my English improved by studying Latin.