(Not a dad but would love your insight) My 2yo nephew I live with cries uncontrollably for hours, what can I do ?

For context my brother, his wife and kid live with me (I’m 19) for a few months while they move houses. The 2 year old was sick and stayed home for a few days but is now getting better and every night when it’s time for bed he throws the most random tantrum, non stop screaming and throwing himself around on the floor for an hour minimum Will not listen to anything or anyone, his parents try their best to stay calm, offer comfort, distraction, listening everything They eventually get irritated and yell at him, he cries more and it doesn’t stop until he falls asleep. They’ve tried leaving him with me alone to see if it could help but he cries for his mom. And his screams are so loud he can’t even hear me trying to talk or sing something calm. When we ignore him it gets worse. (He also screams NO when we ask him questions and he can hear them) But the worse is in the morning since she has to get him to daycare before work and he does the exact same thing to get dressed. He refuses to wear anything, takes it off as soon as it’s on. And I mention this because ignoring him isn’t an option. He won’t stop and they won’t make it on time. My mom (abroad but really involved) has been telling me to help them instead of isolating in the basement but I genuinely don’t know what I can do. I’ve never had kids lol. I’m barely an adult. I love this community a lot as seeing the dads concerns and discussions is so entertaining and heartwarming. Gives me lots of empathy for my dad too.

Just wanted some insight as i know you’re all experienced in this topic, thank you.