Our daughter was doing this for the past 6 months. She has stopped, thank god, in just the last week.
We bought her a light for her bunk bed. So, after her little brother is asleep, she gets to climb in bed with a few books. We give her an allotted amount of time, and then the light is taken away. Since we've been doing this, she has been falling asleep about 90 minutes earlier! Also, since moving her to the top bunk bed, she has to fix her own sheets. It's been brilliant. Before she would mess up her sheets repeatedly and then call for us, and call for us, and call for us.
So, my suggestion is to make a list of all of his "things," and make sure they are all taken care of before you say good-night. Then, keep it emotionless and simple,"good-night, love you."
I also suggest putting the little guy to bed 15 minutes before his brother to give him a chance to fall asleep. We read them both two books, then the little one goes to bed, and our oldest then gets one more book. She then goes pee, has a drink of water, etc. She has long list of "things." By then her brother is usually asleep and then we let her climb in bed to read.
edited to add: I just read inmy30s response. Her trick worked with my daughter when she did this last year. This time it didn't work.