Ronald "Ronnie" Delgado was the Los Angeles City Attorney and the father of Miranda Riggs.
When he heard Riggs and Miranda were expecting, he became so excited knowing in that he would become a grandfather. But the excitement was short-lived when he heard Miranda was killed in a car crash in El Paso, Texas, when she was on her way to the hospital. He was devastated just the very same as Riggs was. He thanks Riggs for being a loving and loyal husband to Miranda and for bringing her back to Los Angeles to be buried, as the rest of their family resides there. Even after Miranda's death, he's still kept in touch with Riggs.
As of recently, it was revealed in the time of Miranda's death, that when she was murdered by drug dealers, led by Tito Flores, who he refused to have any dealings with. Instead of coming after him and risking out war with the police, Flores sent his henchman Gideon Lyon to go after Miranda and kill her and cover his trails and make it look like a car crash.
Ronnie, being a City Attorney, takes his job serious enough. But also, being a family man, he takes the importance of his relationship with his family even more serious. Having Riggs as a son-in-law, he expects Riggs to stay in touch with him as much as possible. As much as he cared and still does for Miranda just as Riggs did, he misses her a lot just like Riggs does.