Looks like there are no more seats for a direct train from Frankfurt to Koln Hbf. All options will need a train change at Koln Messe/Deutz. I will just have a few hours stopover in Cologne, and then onwards to Amsterdam.
How easy is it to make the transfer at Koln Messe/Deutz station for 2 passengers with 2-3 luggages? What should be the minimum connecting time to allot for the transfer?