Enemies at the Royal Altar by Natalie Anderson

Stepbrother. Nemesis. Royal husband! Ever-obedient Princess Tilly is drowning in searing shame, all thanks to a humiliating, viral hoax. To restore the kingdom’s honour, she’s ordered to immediately wed the king’s abhorrent choice. Her long-loathed stepbrother Alex’s alternative? An emergency walk down the aisle — with him instead! Alex can finally exact revenge on his wicked father by whisking Tilly to his fortress island. Rattling the aggravatingly perfect, repressed princess is the icing on the wedding cake. Until hot, fierce fury leads to one devastating kiss and Alex discovers Tilly’s a passion-bomb! Can they control their hate-fuelled heat before it combusts?