Actually the post war sequence are very haphazard and mixed up so can't say really what happened to other sons of pandavas . I even have my doubts on the existence of upandavas since their birth order does not makes sense to me specially when abhimanyu is mentioned as the heir. Or maybe they existed as but were kids of pandavas with their other wives adopted by krishnaa ( princess of panchal) along with abhimanyu as her own and who were not crown prince because their mothers belonged to lesser known kingdom and alliance with dwaraka would have been strengthened by making Abhimanyu the crown prince
Or they did existed were very much krishaa s kids prativindhya was the crown princea and Abhimanyu being crown prince is later interpolation