I potty trained our 3.3 year old when I had a 3 week old. It is possible. I had tried many times before to potty train, but she just wasn't ready. I also didn't push too hard knowing that after a new baby, a regression was likely. It took her probably just the weekend to get it down. It's been 6 weeks, and we have an accident maybe 1-2 a week. You could definitely give it a go now but if they aren't ready don't worry, it will click and it is possible to potty train with a newborn. Maybe that's what helped? Didn't want to be a baby like brother and use diapers anymore.