I have not submitted the application yet. I will be sending the completed application next week. I am only lacking in income requirement of about 1800$ for the year 2014.
I there a chance if i can add my brother later on next year in 2018 and showing that i meet the last 3 year (i.e. 2015, 2016, and 2017 income) requirement
In this case, you don't qualify at all. You must include your brother in family size, and meet that family size going back to 2014. Even if you're $1 short in 2014, your app will be rejected later on. It's a yes or no question if you meet income or not in all qualifying years, there is no discretion allowed by the visa officers.
You will need to try again for lottery in 2018, though keep in mind they may request 2014/15/16 income again if 2017 returns are not completed when they accept apps this year.