I believe Martin Guest, R265, though I think Lucinda married him well after Lily was adopted. That's always been somewhat murky.....
Here's what Soap Central says...
Lucinda Walsh came to Oakdale with her teenage daughter, Lily. Upon arriving in Oakdale, Lucinda tried to steal Whit McColl's newspaper from him since she blamed him for her ex-husband's suicide. She also started a rivalry with Dr. John Dixon for a seat at the hospital board. Lucinda seemed fearless, until she learned about the coup in Montega. Lucinda was afraid for the life of her "goddaughter" Sierra and sent one of her employees, Craig Montgomery, to rescue the girl. Soon, John learned the truth: Sierra was Lucinda's daughter. Lucinda tried in vain to keep the truth from Sierra so that she wouldn't be hurt, but in the end, Sierra learned the truth and they eventually formed a close mother-daughter relationship. At the same time, Lucinda tried to discourage Lily’s relationship with Dusty Donovan, John’s ward, since she felt that Dusty was a bad influence on Lily.
With the arrival of Sierra, the truth of Lucinda's past came out. Lucinda was actually born Mary Ellen Walters and grew up poor in Peoria, Illinois. Mary Ellen's mother sent her away to live with her father when she was about 15. Mary Ellen ran away and ended up in Montega, South America where she married the powerful Jacobo Estaban. Though the marriage provided her with some prestige, there was no love and soon she found herself falling in love with another man. When Jacobo learned that she was in love with another, he banished her from Montega and kept her away from their daughter, Sierra. Heartbroken, Mary Ellen changed her name to Lucinda and married the man she loved, Martin Guest. Martin and Lucinda adopted a child, Lily. Soon after Lucinda learned that the adoption was illegal, Martin killed himself. Later, Lucinda married wealthy businessman James Walsh. When Walsh died, Lucinda bought his company out from under his weak-willed son.
Sierra's parentage wasn't all that Lucinda had to deal with. She also had to deal with the secret of Lily's parentage. Lucinda had never told her teenage daughter that she was adopted. Suddenly, in mid 1985, Lucinda started getting anonymous phone calls, for Mrs. Martin Guest, and saying they knew all about Lily's illegal adoption from baby broker Clifford Breyer. It didn't take long for Lucinda to come face to face with the voice--it was a young woman named Marie Kovacs who tried to blackmail Lucinda with the information. Although Marie was able to get Lucinda to write her a check for $500,000, she was shocked when an angry Lucinda just tore the check right in front of her face! Days later, Marie wound up dead and, after an anonymous tip from Marsha Talbot, Lucinda was called into the police station for questioning. Fortunately, she was quickly taken off the suspect list. Meanwhile, Lucinda had to deal with Lily's involvement with stablehand Holden Snyder. Lucinda felt that the Snyders weren't good enough for her daughter and she tried everything to keep the young couple apart. In 1986, Lucinda was shocked to discover that Lily's biological mother was none other than Holden's adopted sister, Iva! Though both Lucinda and Iva tried to keep the news from Lily, she finally found out the truth in 1987.