Here are the KS requirements for Common Law Marriage.
I also have two links below for additional detail.
Under Kansas Statute 23-2502, both parties to a common-law marriage must be 18 years old. The three requirements that must coexist to establish a common-law marriage in Kansas are: (1) capacity to marry; (2) a present marriage agreement; and (3) a holding out of each other as husband and wife to the public.
Kansas recognizes common law marriages contracted by persons within the state and those who contract common law marriage in another state that allows couples to marry at common law.
http://marriage.laws.com/common-law-marriage-kansas
https://www.ksbar.org/page/marriage_divorce