Flyboy by Rhian Cahill

All Alyssa Drummond wanted was to be awarded permanent guardianship of the sister she never knew she had. Now she’s not only dealing with a hormonal teenager. There’s her vengeful alcoholic mother, an evil stepmother and a marriage of convenience to her best friend with benefits.
Oh, and that best friend? He’s been hiding things.
Like Jack Townsend isn’t his real name, or at least not his full name, and Montgomery Jackson Winchester Townsend III happens to be the billionaire heir to one of the world’s largest corporations.
And that marriage of convenience? It comes with a lot of inconveniences starting with a security team who put the secret service to shame.