Fight Club

I swear, its like kiddie fight club in my house these days.  (I know, I know...The first rule about fight club?  Never talk about fight club.  Still.)  Andrew and Hannah's sibling rivalry seems to be at an all-time high.  Yesterday Hannah woke up, came downstairs, and walked over towards Andrew's toys.  His response?  Smack her in the face.  ?!?!  He has never done that before, so I was shocked.  Hannah promptly pushed him back (that girl is NO easy win!) and then they were both crying.  Chris, being the fabulous guy he is, had let me sleep in but I couldn't help but wake up when I heard the crying.  By the time I got up and got my lazy butt downstairs, they had both been sitting in time-out for a good while and were on "Level 3."*
The rest of the day kind-of went the same way.  We had some periods of happiness, especially when Poppy and Nana (my dad and stepmom) arrived for their visit, but for the most part the kids have been at each other's throats more than ever before.  I was thinking that, with Andrew in school all day and Hannah at preschool, the time apart would help make this stuff better.  Not happening.  Hannah goes to preschool from 9-12 every weekday, with two days a week when she is there ALL day (picked up after Andrew gets picked up from school).  According to Chris she is fantastic when its just them, but as soon as Andrew gets picked up she gets CRANKY.  I guess she just wants to be the only child or something.  She's definitely not a fan of sharing attention.  Andrew is usually sweet, but oh.my.lord...if Hannah dares get anywhere NEAR his toys?  Meltdown!  He cries and cries and cries...I keep telling him that the more he freaks out, the more she wants to keep doing whatever it is she's doing.  Its as if they LIVE to annoy each other.
I don't know what the solution is, or if this is just a phase, but I am ready for the fight club to be shut down.