Booking.com parent company also owns: Priceline, Agoda, Rentalcars.com, KAYAK and OpenTable. It also has "subsidiary brands": Rocketmiles, Fareharbor, HotelsCombined, Cheapflights and Momondo.
It's worth noting the while some of the other brands may be more well known in the Americas, Booking.com is actually the vast majority of the business. That's the reason why the parent renamed from "Priceline.com" to "Priceline Group" to "Booking Holdings". (Source: I'm a former employee)