Check the website for faculty profiles. From what I can tell, John McMillan, Robert Flanagan, Peter Henry do something related to development. I'm not interested in behavior, so I'm not sure who does that.
Why do you ask? The
SoP prompt doesn't really require you to explain at length about why you want to attend their particular program. I mean - it's Stanford: of course you want to attend, and they know it without you needing to explain it.