His Lover's Little Secret (Millionaires of Manhattan #3)
Andrea Laurence

When a chance run-in forces Sabine Hayes to confront the father of her son, she refuses to give in to Gavin Brooks and his demands. There was a time where his power and wealth impressed her–even intimidated her–but not now. She will let him get to know his son, but she won't go back to Gavin's privileged world...or his bed.
Gavin never stopped wanting the purple-haired yogi with the the nose piercing and the ability to challenge him like no other, but he let her go because that was what she wanted. Things are different now. He has a right to claim what's his...and he'll do anything to keep Sabine and their son from slipping through his fingers a second time.