Nice to see a game rated T for Teens turn to this gay romance game because...hey sims 3 has it. I don't know about you but I don't want my son exposed to SGR.
Believe it or not, Same Gender and Opposite Gender romance have absolutely Zero bearing on the ESRB Rating of a game. It's strictly for the Romance only. (This clarification is listed earlier in this thread; you can find it if you really look for it.)
So what are you going to do if your son is exposed to this situation in the "Real World" as school? Just hide your head in the sand and hope it goes away? Or will you talk to him about it and explain your feelings and how think he should deal with it?
As others have mentioned in this thread, It's not up to EA or Bioware to parent your children, that's entirely up to you.
Seems to me, SGR being added to game would be an excellent time for you to talk to your child about it.
On a side note, Most Teen level children are already completely aware of what Homosexuality is and most likely already know at least one person who is. Since your Son plays this game, we can safely assume that he is at least 13 right?