Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 26
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Human Factors; Procedure; Company Policy
I was working at the sector and noticed an alert on my display on three aircraft coming from the adjacent Center. It indicated that Aircraft X; who was level at 35000 feet was in conflict with Aircraft Y and Aircraft Z both climbing to 35000 feet all coming from the same adjacent Center sector.  Their 'controller' ended up stopping both Aircraft Y and Aircraft Z at 33000 feet. The problem was Aircraft Z was behind Aircraft Y and 160 knots faster. I alerted the underlying Sector controllers to the large overtake. As soon as Aircraft Y came over; the underlying sector controller stopped Aircraft Y's climb at 31000 feet. If we had not noticed the overtake; separation would have been lost approximately 10 to 15 miles outside the other ARTCC airspace. Retrain Center controllers and hold them accountable for their mistakes.
ZMP Center Controller reported the adjacent Center was handing three aircraft off that were on conflicting headings and in an overtake situation.