To tell parents or not

I am 28 and married i have 1 baby boy and my parents were thrilled when they knew he was coming. However a few months ago they told me that i should not have another kid because its easier with one and they say look at how my sister turned out (we arent very close and she is selfish sometimes and rude) I may be an adult but for some reason I am always abiding. however out little family is growing. i just found out that i am pregnant with baby #2... idk what to do...seema easier said than done....to just not care what they think...