This is kind of a fun article that I ran across this morning:
http://www.petmd.com/cat/behavior/evr_c ... _07042017#What I see a lot between my two bengals, is that it's definitely a social thing. The typical pattern is that Serafina or Gaga will be snoozing somewhere, or about to settle down, and then the other one will appear. There will be a tense moment while they decide whether the other one's presence is accepted or whether they want to be alone, and if no growling or hissing or paw swatting happens (usually Serafina throwing a tantrum), usually Gaga will make the "peace gesture" by licking her sister a couple of times on the face, then all is good. It's kind of like she's saying "Chill sis, everything is cool".