I will give you one hint. Tucker belongs to Luke Prescott, a major character toward the end of book 2.
In other news, I have been compiling the "Ranch Stories" from the blog and editing and formatting them to be included in a new short-story collection I hope to pitch to Kregel the end of March. Yes, there are many stories in that book you have read here on the blog. However, for sure there are three new ones: "Britches Are Not for Little Girls," (the story of why Andi is allowed to wear overalls, when that was certainly not the norm), "Where the Trees Meet the Bay," (when Andi boards the steamer, Yosemite, and goes to Tacoma to visit Jenny.) Ever since nearly drowning at the end of Family Secret, Andi hates water. Tacoma is on Puget Sound. Wait till you see what happens! The other new story is "Hurrah for the Fourth of July!" The story of the Fourth of July race Andi ran with Cory just before Dangerous Decision, and how it came about that she was in the race in the first place. Things are not what they seem . . .