shark teeth ?

Rose • Hiiiii
Sorry don't know where to put this subject .... my son to start with when he turned 7 he started to get adult teeth growing behind baby teeth and they're all wonky he's had several baby teeth removed to make room for the adult teeth he has to go back again for more taken out as they are getting worse more and more adult teeth keep coming ! The dentist said it was the case of shark teeth he has seen ... now onto my daughter she's only 5 ! no holes or anything in the baby teeth they brush daily 2-3 times with adult tooth paste .... she's getting them now ! does anyone know why it occurs ? she pulled her baby tooth out as the other made it wobbly now the one next to it has popped through ! within a week ! she's going end up with all wonky teeth too ... no one on his side of the family had this and no one on our side either ! does anyone know what can cause it ? or what I can do to stop it daft as it sounds she's only 5 her teeth arnt meant to be falling out yet x