Santa or Father Christmas?

Depending on how you look at it, either Scottish and English are separate "Anglic" languages or Scottish is a dialect of English. Linguists take both approaches because the difference between a dialect and a language is political and social, and not something innate. The old joke often made in the context of Yiddish (either a German dialect or its own language) is that "a language is a dialect with an army and a navy". Scottish has a rich history as a court and legal speech and as a literary speech too, so it is perfectly correct to call it a language from that perspective, just as it is probably correct to call it a regional dialect from another perspective, particularly after the act of union. Either way, this is not a matter of three languages sharing a root equally. Scottish and English do not just "share a root". They are effectively the same speech, descended from Old English (which had its cultural flowering in northern England and southern Scotland) as it developed following the norman conquest. Scottish has a slightly different mix of borrowings from Danish and Irish languages when compared to the Midlands and East Anglian varieties of English from which the standard British and American English-es developed, but the differences are minor and they are mutually intelligible in all their forms. Dutch, on the other hand, is a linguistic third cousin to the Anglic languages, and is not mutually intelligible with them. Dutch, Frisian and Flemish are linked to English and Scottish because they are all West German languages, but that's a root in the distant past. The suggestion that Scottish is closer to Dutch and Southern English varieties of English is nonsense.