Ben Tennyson & Gwen Tennyson have one of the closest relationships

While not twins, Ben & Gwen were born on the same day in December, causing their long-standing rivalry way before they were 10 years old. Their rivalry was evidently petty & childish in many ways, as they didn't speak to each other for two months over an argument about a stick of gum and had gotten so bad that their parents refused to take vacations together anymore. Their gene somehow gave birth to Zach.