Tycoon's Instant Daughter by Christine Rimmer

Cut from the same rawhide as his infamous father, Cord Stockwell was ruthless in business — and love. So when social worker Hannah Miller claimed that three-month-old Becky was Cord’s progeny, he struck a deal that brought baby and Hannah into his opulent home. The wealthy bachelor soon set his sights on something he wanted more of...the sexy temporary nanny! Still, Hannah insisted she had zero interest in intimacy — but her passion-filled kisses betrayed her. And Cord would not be denied. He’d darned well marry Hannah to keep the upper hand!