Is this just a baby thing

My brother has been coming around to visit since little lady was born. She is a yr old and my brother has come by to visit us every Wed. She has not warmed up to him at alllllll. He plays with her talks to her etc...And she doesn't want to be bothered with him she acts scared of him. Tonight we were out to dinner and she cried when he came by her.... What is this about? My family and I are starting to worry because it's very very weird... shes a friendly baby and laughs with strangers. Anyone have any ideas...is this just a baby thing?