Read Blake Snyder's book, "Save the Cat". Before you try making anything, you need a script. Before you can write a script, read "Save the Cat".
And work on your log line. You've told me about the ages and relationships in that description, but what is the conflict? Are the half-brothers radically different from the adults? Is the conflict over learning how to be a parent suddenly, or is there something more sinister following the boys into the household? You gotta spell it out and make it interesting if you want to excite potential investors with your pitch.