Complex sentence: His sister Michelle had begun dating her law firm colleague, Barack Obama, who played basketball recreationally; she asked her brother to play with him and give her a character assessment, so that she would know whether she could become serious with him.
Split into simpler sentences: His sister Michelle had begun dating her law firm colleague, Barack Obama, who played basketball recreationally. She asked her brother to play with him and give her a character assessment so that she would know whether she could become serious with him.