Bought for the Marriage Bed: Harlequin comics

Nina's twin sister, Nadia, is a vindictive gold digger. The only good thing Nadia's ever brought into this world was her daughter, Georgia, of whom Nina is very fond. When Nadia's devilish ways threaten to separate Nina from her beloved niece, Nina does the unthinkable. She pretends to be Nadia and agrees to marry Marc Marcello, Georgia's uncle. Marc is a notorious playboy and their marriage would be in name only, but Nina is left with no other options—she'd do anything to save Georgia from growing up in foster care.