title: Contribute to different repos forked from same repo
body: <p>I'm quite new to GitHub and git, and I'm trying to figure out how I can contribute to different forks of a repo when they have been forked from each other. This is how the structure of the forks look:</p>
  <ol>
  <li>Repo_A (original repo)</li>
  <li>Repo_B (forked from Repo_A)</li>
  <li>My_repo (forked from Repo_B)</li>
  </ol>
  <p>Even though Repo_B is forked from Repo_A, it has evolved and differs from Repo_A. I am mainly going to contribute to Repo_B, but there might be some lines of codes I would like to contribute to Repo_A. Is there a way to do this without making two accounts and fork each repo?</p>
  <p>I've been searching for answers and looking at different solutions without any luck. This is what I have tried so far:</p>
  <ul>
  <li>Forking Repo_A, making a pull request, then removing Repo_A and
  forking Repo_B. This method works if the changes is being commited.
  If not, the pull request will be automatically closed when the repo
  is removed from my account. It also feels a bit tedious to having to remove the repo and fork it for each time.</li>
  <li>Making a branch in My_repo with the
  single file I want to edit. Then copying the code from Repo_A, making
  the changes and sending a pull request to Repo_A. The problem then is
  that the history doesn't seem to be includeded and all the code is
  considered new lines (even though I only changed some characters).</li>
  </ul>
  <p>I think I'm onto something with making branches.  But is it for example possible to make a branch in My_repo that has a file from Repo_A? And is it even possible to be contributing to both Repo_A and Repo_B from the same account even though they have gone different ways in development?</p>