My youngest brother in law, used to start crap like that with my sons...they were 11 and 13. They'd kick his a$$ everytime. Then he'd run to my mil, and whine my kids were being disrespectful...after he started it...ugh.
The best was their response to my bil asking my 13yo son about having a gf, they called him the "30year old virgin". Even my dh laughed.
My bil is such a jerk.