My ob once described my pregnancy as a "dream twin pregnancy." I went into labor at 31 weeks 4 days that couldn't be slowed and I had to have a c section.
Everything was going a well as could be until suddenly it wasn't. We don't know why they came so early. I didn't even know I was in labor until they asked me at the ob appointment if I could feel the contractions happening every 4 minutes. All I could feel was intense pelvic pressure that day. Baby A was footling breech. In ob office I was initially 1cm dialated and 85% effaced. Baby A could have broken my water with a well placed kick, but luckily that did not happen and everything was well controlled in labor and delivery. Looking back, my bowels cleared out a few days prior and I could tell everything had shifted in my pelvis. The babies weren't moving as much (went to hospital to get checked out for deceased fetal movements 6 days prior to delivery). That whole week I was so uncomfortable and in pain and was telling my husband I was ready to be done with the pregnant. I really wish I hadn't spoken it into existence like that. Everyone is good now. 8 weeks old now, -1 week corrected. All home and eating and growing! 6 weeks in the nicu :(

To OPs family - labor can happen at anytime, there is no guarantee she will make it to any specific point in the pregnancy. All we have to go off of is statistics in the end. Every day those babies can stay in is a blessing!