Couvade syndrome is when a dad-to-be feels like he's having pregnancy symptoms too. Mommies are the ones who usually have a baby in their belly, but sometimes daddies feel like they're having one too. It's kind of like when you play pretend and act like you're a mom or a dad, and you pretend to have a big belly too, just like the mommy.
Some daddies might feel sick to their stomach, tired all the time or even have cravings for certain foods, just like mommies do when they're pregnant. This happens because daddies are so excited and happy about the new baby, that their bodies start acting like they were the one carrying the baby!
It's perfectly normal and nothing to worry about. It just shows how much love and connection dads feel with their unborn babies.