Just this past week Max and Aviva have started playing together. The first time we were in the living room and Max crawled over to Aviva and put his head in her lap. She giggled and pushed it off and crawled away. He did the same thing again and she started laughing and responded the same way. The did it 4 or 5 times and I was so pleased to see them interact.
Previous to this week, the most interaction they've had is in the car if Max is in a bad mood. Aviva will squeal and Max will yell, "STOP YELLING, AWEEWA (Aviva)." She thinks it's a game, laughs, and does it again. He of course screams at her again and this goes on and on.
Yesterday they started playing chase and hide and seek together. It doesn't last long, and it usually consists of hiding on the other side of the door, but they both love it and I couldn't be happier.