Anytime they interact. DD2 is 4 months and DD1 is 16.5 months. Yesterday DD2 rolled back-to-front for the first time and she's been doing it constantly since. DD1 started helping her roll and then getting down on her tummy and propping her own head up to look her sister in the eye. So freaking cute.
Re: Fave Things about 2u2
<a href="http://s5.photobucket.com/albums/y161/putalittlepolkainyourdot/?action=view
Matching jammies (and sometimes outfits when I can't help myself!)
DD1 saying "She my sisser and I looooooove her"
The way they love to give each other hugs and kisses
DD1 comforts DD2 if she gets hurt or is upset.
The way that they giggle at each other and keep each other entertained.
DD1 sings songs to DD2 and DD2 will stop whatever she is doing to listen to the "performance".
I really love everything about it... now that we are out of the very early stages on 2 kids 13.5 months apart!