The Umli? Did/ do they exist?

[Thinlómien]

I´ve been thinking this for long time. Umli, those half-dwarves, living in cold areas, do they exist in Tolkien´s books? They are one of the playable races in M.E.R.P. (Middle-Earth roleplaying), but I haven´t found any mention about them in Tolkien´s books (LotR, Silmarillion, Hobbit, Unfinished Tales). So I ask you, who I suppose to know this, is there any mention about umlis in any other souce, eg. The Adventures of Tom Bombadil? I think the idea of some half-dwarf folk sounds strange but it also sounds strange that the makers of the roleplaying game would have put races of their own to the book (I think it was made in co-operation with someone owning the rights of Middle-Earth...?).
And you may ask that why did I put this here, not to the roleplaying board. The answer is simple: I suppose you, who visit here know more...