A man in The Bronx splashed relatives with sizzling hot oil on Friday, burning his 2-month-old grandson and sparking a fire in the family’s apartment, according to police. 41-year-old Ricardo McDonald got into an argument with his 19-year-old daughter and 18-year-old son around 10:30 a.m., which is when he began flicking them with hot oil from a cooking pan, the sources said. McDonald’s daughter was in the family’s living room holding her 2-month-old boy, who was also burned.