The answer to the question: Who is Rebeeca's dad? is inside the article: Cattle, timber and mining baron George Washington "G.W." McLintock is living the single life on his ranch. He is estranged from wife Katherine, who left him two years before, suspecting him of adultery. She has been living the society life back East while their daughter Rebeeca (whom G.W. calls "Becky") (Stefanie Powers) is completing her college degree.  Following a meeting with a group of homesteaders whom he cautions against trying to farm on the Mesa Verde: "God made that land for the buffalo. It serves pretty well for cattle. But it hates the plow! And even the government should know you can't farm six thousand feet above sea level!" He hires one of them, attractive widow Louise Warren, as his cook and housekeeper. G.W. welcomes both her and her two children into his home, including grown son Dev, who is handy with his fists, good with cattle, and is an excellent chess player, who had to leave Purdue University on account of his father's death.  Katherine (a.k.a. Katie), returns to the town of McLintock, seeking a divorce from G.W.  He declines to give her one, having no idea why she has been so angry with him and why she moved out two years ago. Following a misunderstanding which leads to a Comanche subchief nearly being lynched by a hotheaded settler father who believes his daughter has been kidnapped, there is a gigantic brawl at the mud slide by one of McLintock's mines. Significantly, Katherine is in there swinging on her estranged husband's side as the local Indians watch the white folks make fools of themselves., can you guess it ?
The answer to this question is:
George Washington "G.W." McLintock