When a legal representative, or trustee, or other representative appointed under any agreement, trust indenture, will, or other instrument in writing has been duly appointed for any person under disability and such legal representative, or trustee, or other representative does not promptly, after demand therefor by the person under disability or anyone for him, take action, then such person under disability by next friend may take action before the expiration of the periods fixed in this article for the taking of such action by any person under disability, or his legal representative, or trustee, or other representative, but not thereafter.
C.R.S. § 13-81-105