Matthew was 3 minutes older than Michelle, they are twins, brother and sister.They like to compete for toys, mom's attention. If Matthew gave me one book about vehicles to read, Michelle would not be happy since she wanted mom to read another book. At the end mom had to read to sister, brother was easy to handle.They fight for toys, sometime bite each other. It happened outside the house as well, such as in daycare, and in ontario science museum. Mom has to tell Matthew firmly: no fighting, no biting.They start to realize that they are brother and sister, if one cries for something, the other would give up the toy to one who cries.