What are the sister languages of English?

English is mostly a Germanic language, with strong French (Romance Language) influence. So you might consider any of the other Germanic languages to be sister languages to English. These include:

• German
• Dutch
• Yiddish
• Africaans

Answer

English's sole sister language is Scots (not to be confused with Scots Gaelic [a language spoken in the highlands] or Scots English [a dialect of English spoken in Scotland, particularly in the east central belt and the borders region]).

While English may be related to other languages, such as Frisian, Dutch, or German, these languages have not developed alongside English - and have thus lost their sistership and the level of understanding they once had with English. There can still be a level of understanding between English Speakers and Scots Speakers today if they tried, similar to Portuguese Speakers and Spanish Speakers or Irish Gaelic and Scots Gaelic Speakers.

However, you should note that the level of understanding is not consistent across Scotland. Scots is split into three Dialects; Lallans spoken in the Central Belt, Lowlands, and west coast, Ullans spoken in Northern Ireland, and Doric, spoken in Grampian and the east coast. If you speak English, the easiest dialect of Scots to understand would be Lallans - Ullans would be fairly harder to understand, and you haven't got a snowball's chance in hell of being able to understand Doric :)