If you're looking for a meeting place or a good stop around ½ or halfway between Groesbeek and Aachen, you can try Viersen, Germany, which is almost an hour southeast of Groesbeek, or almost an hour north of Aachen.
About ¼ or a fourth of the way, you can stop at Venray, Netherlands. This is about half an hour south of Groesbeek.
About ⅔ or two thirds of the way, you can stop at Juchen, Germany. This is about 1 hour southeast of Groesbeek, or about half an hour northeast of Aachen.
If you drive straight through without stopping at all, the total distance is 155 km. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 1 hour, 41 minutes.