You need to define "RV". If the RV is a motorhome, no problem. But if it's a trailer, then it depends. It's called triple towing (tow vehicle, first trailer. second trailer), but most call it pulling doubles or double towing.
Rules vary by state. In most states, triple towing requires that the first trailer be a fifth-wheel. You cannot pull two "bumper-pull" trailers. So no TT plus a boat. Also. total length restrictions vary by state, with 65 feet max being common. But most states won't bother you for length violations unless you do something else that gets their attention, such as a wagging trailer or an obviously overloaded tow vehicle.
Grumpy ole man with over 50 years towing experience. Now my heaviest trailer is a 7,000-pound enclosed cargo trailer, RV is a 5,600 pound Skyline Nomad Joey 196S, and my tow vehicle is a 2012 F-150 EcoBoost SuperCrew.