The Introvert’s Prince by Caroline Lee

They call him The Playboy Prince, and Viggo Magnusson doesn’t really mind. After all, he’s spent the last seven years carefully cultivating that persona and reputation…all to hide his greatest secret.
His son.
But now, only days before his mother’s remarriage and a royal wedding event of a lifetime, Viggo has decided to share this secret—little Stefan—with his family. But for that to happen, Viggo must convince his co-conspirator, the boy’s caretaker and guardian, to go along with the plan. The only problem is that his well-known charm isn’t going to work on this particular introverted lady.
Marcia Lindqvist has been willing to stay under her father’s formidable thumb in order to protect and care for her nephew, seven-year-old Stefan. The boy might not be physically perfect, but he is her entire world…well, him and Prince Viggo, who is in their lives as much as Marcia’s father will allow.

But Marcia has spent her life as a wallflower, watching The Playboy Prince woo his way through the kingdom. Is there any way they could be happy together? All it will take is a few leaps of faith, and they both could get what they want…

But it will take Stefan being in danger to show them what they need.