418 brat son of BF...

Do yourself a favour. RUN!

Really, if you expect to come first in a relationship where kids are involved that do not belong to you, you are sadly mistaken. Of course he spends time with his kid on the weekends that he has them and he SHOULD! Also, non-custodial parents tend to be lax when it comes to discipline because the time they have with their children is so limited, that they are afraid to "damage" any relationship they may have with that kid. Especially if it is a teen.

I'm with Nooner on this one: Run fast and run far.

Your biggest problem isn't the kid:

"He tries to get in between my bf and me all the time. []He whines and gets his way.[] (Emphasis mine.)

Kids will whine to get their way; it's been happening since the beginning of time. Your problem is that Duddy/boyfriend doesn't have a spine.

When I was single, I didn't categorically rule out dating parents, but I realized there were only about 5% I could tolerate dating.

Maybe they left Mumsie for good reason or maybe they got left, but in my experience, most single Duddies are guilt-ridden pansies with hellions in tow. No thanks.