* Estonian: While not mutually intelligible, Estonian shares a high degree of similarity with Finnish in terms of grammar, vocabulary, and sound system. They are considered sister languages.
* Livonian: A critically endangered language spoken in Latvia, Livonian is also closely related to Finnish and Estonian.
Other Finnic languages, like Karelian, Veps, and Ingrian, are also related to Finnish, but the similarities are less pronounced.
It's important to note that Finnish is not related to any of the major language families of Europe (like Indo-European or Romance). While some grammatical features may seem similar to other languages, these are usually cases of convergent evolution (languages developing similar features independently).