The Eustachian tube connects the throat and the middle ear (the site of a typical  ear infection ) and allows air to travel between them and equalize the pressures. When the Eustachian tube is temporarily pinched off, pressure can build up in the middle ear.
Visitation is a matter of state law, but generally speaking, every state allows parents to exercise a reasonable amount of visitation with their children, which generally means enough time to establish and maintain a meaningful relationship.
A custodial parent who doesn't honor the standing visitation order is in contempt of a court order and the court can order a modification of the custody order if the contempt continues. A child cannot refuse to visit the other parent until they reach eighteen years of age in virtually every state in the United States.