Romance Hero and heroine have short fling, she's pregnant, he lied about his name

Hi all,
This book is part of a series. First there was a series about three siblings with rich family, the books are about how their grandmother (dad's mom) sets them all up with love. Then came this specific series, turns out that the dad had a second family, and had three kids, now the grandmother is setting up these kids. It was category romance, I think Harlequin desire but could have been Harlequin Presents.

Ok, the actual book.

- Hero is rich. He goes "undercover" at one of the resorts his family owns to check on how good they are. Heroine is there on a vacation. They hook up. He gives her the fake name he went undercover with.
- He gets a message that his sister was hurt and disappears, not even leaving a note.
- Heroine is pregnant. She can't find the hero cause she doesn't have his real name.
- Heroine is a kindergarten/preschool teacher. The grandmother sets her up with her own preschool in Denver. Which is of course where the hero lives.
- Hero's nephew is in the preschool and getting into trouble. Hero comes to school to talk to the owner, the heroine. They meet again.

Amazing that I can remember all these details but not the name :)

Thanks!