Okay, I just feel that people are still asking so Im gonna say the truth

Is Stewie Griffin Gay or Straight?

Stewie has yet to decide whether he is gay or straight. For now he plays both parts.

Does anybody understand what Stewie says?

Yes, the Griffin family and every other character indeed understand what Stewie says, but considering the fact that he is a 1 year old baby nobody takes what he says seriously.