Small babies

Im trying to get some reassurance because people are freaking out but my baby girl is 3 months old and weighs 10lbs 10oz. She is pretty small. My side of the family has history of small babies including my nephew. My baby was born at 5lb 14oz at 40+4. She is breastfed exclusively. Since her 2 month appt she only gained 10oz. People keep telling me she isn't fed enough and i should give her formula bottles. A baby born 6 days before her weighs 15lbs. She has normal diaper outputs, eats when she wants, and is happy. Anybody else out there with just small babies???