Need your 2 cents

I have just got my I140 approved and I am preparing for I485 petition. I heard if I file I485 for my boyfriend, he will also get a chance to get I485 approved. Since we have to get married first in order for me to claim him as a dependent, is this a risk for my I485 petition? Because I also heard that , if I get married now (right after my I140 approved), the Services will suspect the purpose of our marriage.

Thank you in advance for your input.