My DS (also 16 months) went through a major hair pulling phase, and 6 year old DD took the worst of it. For awhile DD and I both kept our hair covered pretty much all the time at home just to avoid some of the hair pulling. That cut down on it a lot. I also taught her to gently grab his hand, poke her finger in to break his grasp, tell him "I don't like that. Be gentle," and then refuse to play and walk away if he continued. I intervened when possible, but there were times that it took me a minute to get to them (like when I was in the bathroom), and he'd yank out handfuls of her hair, so for that reason alone, it was very useful for her to know how to handle it. Also, DS absolutely worships DD. DD being unhappy and walking away from him made a much bigger impact than anything I was able to do. The hair pulling has stopped, by the way. Now if we could convince him that whacking us in the faces with wooden toys isn't nearly as funny as he thinks it is, we'd be pretty happy campers.
