SDCL § 55-4-50: Co-trustee's inability or failure to perform.

If a co-trustee is unable to perform duties because of absence, illness, disqualification under other law, or other incapacity, or fails to perform duties due to inaction or neglect, and action is necessary or appropriate under the circumstances to achieve the purposes of the trust or to avoid injury to the trust property, the remaining co-trustee or a majority of the remaining co-trustees may act for the trust.