Is this really a surprise? And did she ever get a dna test?
From Vanity Fair:
In 1963, Mansfield filed for divorce from Mickey and began a well-publicized romance with an Italian entertainer named Nelson Sardelli—only to reconcile with Mickey several months before Hargitay’s birth in 1964. In her 20s, someone showed Hargitay a photo of Sardelli. She immediately knew in her bones that he was her biological father. “It was like the floor fell out from underneath me,” she recalls in My Mom Jayne. “Like my infrastructure dissolved.” But when she confronted Mickey, he denied it. The encounter was so shattering that she swept the skeleton back under the family rug and never mentioned Sardelli to Mickey again. (Mickey died in 2006.)