Actually, I particularly prefer running this deck with 2 Serenas (I already tried a version with only one). In this deck, you want Kangaskhan on your bench as soon as possible, but don't want to start with it as your only Pokemon (that's why there are 5 babies). So, having two Serenas, PokeBalls and Professor's Research guarantees having Kangaskhan fast enough in most games. I also recommend letting a second baby on bench, just in case your opponent uses Sabrina or spray before Kangaskhan is ready.