Loyal Davis
From Conservapedia
Loyal Davis, M.D. (1896-1982) was the father-in-law of President Ronald Reagan who had been influential in introducing Reagan to conservative principles. Nancy Davis Reagan was Dr. Davis's stepdaughter, whom he adopted after marrying her mother.
In addition to being an accomplished neurosurgeon in Chicago, Davis was a prolific writer and supporter of conservative principles. He was active in several medical societies, including serving as president of the American College of Surgeons for several years, which managed his memorial service when Dr. Davis passed away.