pienemmien
Pienemmien is the genitive plural form of the Finnish comparative adjective pienempi, meaning “smaller.” In Finnish, adjectives decline for number and case, and the comparative form can also take genitive plural endings. Pienempien is formed from the stem pien- with the comparative suffix -empi and the genitive plural ending -ien, yielding pienempien.
The form is used when the adjective modifies a noun that is itself in the genitive plural,
In practice, pienempi remains the base comparative form, while other related forms include pienempien (genitive plural),
See also: pienempi, pienemmät, pienin, pienempiä, pienempien talojen.