Lone Star Rising by DARLENE GRAHAM

Another man's baby
After her husband is killed in a barn fire, Robbie McBride Tellchick is left alone to raise three boys–and the baby on the way. With the fire still under investigation, she can't even depend on the insurance money. She can, however, depend on Zack Trueblood, a firefighter who claims he wants to help Robbie through her pregnancy–and beyond.
It's well-known in the town of Five Points, Texas, that Zack's ambition is to be a landowner. His growing feelings for Robbie seem more than sincere, but she has to wonder what kind of man wants to raise someone else's child. Does he want the land she can no longer afford to keep?