The Kardashian-Jenner sisters have filed docs to trademark the names of their kids -- Saint, North and Chicago West along with True Thompson and Stormi Webster. In docs, obtained by TMZ, their mommas say they want to slap the kids' names on a number of products ... including a clothing line, toys and skin care products.

Kylie in particular also filed a trademark for "Stormiworld" -- no big mystery what inspired that move, but safe to say Stormi could take after mom or dad.

What's more ... the fam wants the ability to sign endorsement deals to pimp others' products, although the application doesn't list specifics.

Welcome to the family biz, kids. Now get to work!