Assuming “just before” is within a week of Christmas, all trains are likely to be very full. The last few trips I’ve taken between Belgium and Germany were full even on less peak travel dates, I guess due to aggressive dynamic pricing by the train companies. If you travel extremely early in the morning or late at night you might have better luck. I think the ICE you’re referring to does start in Brussels so that’ give you a better chance of finding seats, vs. at an intermediary station where the train already is full of through passengers. You might luck out, you might not.
As has been mentioned in the comments you have a couple options for reserving seats: either booking your whole journey (tickets+reservation) right on bahn.de or booking the tickets with Eurostar and the making simple seat reservations only on top of the Eurostar ticket booking with bahn.de.
Credit:stackoverflow.com‘
4 Mar, 2024
4 Mar, 2024
5 Mar, 2024