["My sister is pregnant!  I can't believe I'm going to have another niece or nephew", 'That is pretty exciting :) do you have kids of your own', "I have a son, he's one.  I also have one niece and one nephew already"]
Nice looks like you're gonna be racking up some babysitting hours..lol hope you're ready
I just found out my sister is pregnant!  I'm going to be an aunt again!  They've been trying for a while so this is great news.