I am looking for a book about a young widow, living on her inlaws land who comes up with an idea to breed her sheep late so she will have lambs
She has a hard time breaking through the in laws family
Could it possibly be A Widow's Hope, by Mary Ellis? The details aren't exactly as you describe, as it seems the brother-in-law is her main detractor, rather than the whole family, but it's as close as I could get. Please note that the link above only goes to our e-book copy. We don't have the regular book version, but possibly could get it for your via Interlibrary Loan.
If that isn't the title you are looking for, are there any other details that you can remember that makes this story unique? Any other information will help.
Thanks for your question!