Sock buddies-they are each wearing one of David's old soccer socks. David and Lincoln make the best of friends. David will give Lincoln piggy back rides, play games with him, help him change clothes and even read to him. Lincoln is young enough that he is no longer a peer like Mac and Gabe, but more like a toy. It probably helps that he is also a boy too quite honestly. David doesn't have quite the same bond with the two girls yet. It warms my heart to see these two together though.