Yep according to synopses he did pretend to be the baby’s father initially, I believe this was when Liza and Travis initially found out that Cissy was Roger Lee’s mother. This was because Cissy didn’t want anyone finding out that Lee was his father (she didn’t want to hurt Lee and Sunny).
Oh it was definitely because of Ridge, her first lover She crossed the first line when she slept with still married Eric, who was her mother's first love after all. Then she betrayed Eric with Ridge multiple times, and in the following years she would very comfortably use her body to seduce Ridge and Thorne and point out to Taylor or Stephanie that they are too reserved. I loved how the writers made Hope declared virgin in contrast to her mother and how she would call Brooke out sometimes for the sex scandals.
And funny thing, at least three characters told Stephanie that her love for Ridge is rather disturbing - Brooke, Taylor and Jackie - she slapped all three of them for saying that.