Zoey, it sounds like there are a lot of changes in the family dynamics going on.

You just recently lost your dad and it is normal that you are going to feel up and down as you deal with your loss. (((hugs))) That, combined with the hormonal changes that come with pregnancy are likely to make this time tough for you.

The sisters - it sounds like they are still pretty young and perhaps have had a close relationship with their brother? Maybe they are afraid of losing the bond they have because you have become the most important woman in his life.

As a mom of 3, I can tell you that patience is something you will need to develop in leaps and bounds once you give birth. Now is your chance to practice. Take time to interact with your sisters to be. Get to know them in the same way that you would want them to know who you are. Ask them to talk honestly about their fears and their hopes about your marriage to their brother. Assure them that you aren't taking him away - only adding another "sister" to the family.

I hope some of what I've written will help you.