A Family for the Holidays (Prairie Courtships)

Her Guardian Groom 

Paid to accompany two orphaned siblings to their grandfather in Nebraska, Lily Winter is dismayed to discover the old man has gone missing. And when the children's inheritance makes them a target, buying protection is Lily's only option. Until a handsome gun-for-hire suggests another solution: marriage. 

Undercover US Marshal Jake Elder can't reveal his true identity without blowing his mission. Nor can he leave the town's pretty new arrival unguarded. But while uncovering a plot against her charges is difficult and risky, falling for Lily is all too easy. Especially once their marriage in name only gives Jake a glimpse of how wonderful Christmas—and their future as a family—could be.