“Ours” baby

Can any stepmoms out there comment on having an “ours” baby. I’m 31 and my husband is 38. I am currently a childless stepmom and we are trying for our first. I have two SDs 8 and 11 and we basically split the time with them, long story, but both parents are very involved. I have a good relationship with the girls, but all communication about them stays between mom and dad because that’s just what works best for us. How does an ours baby change the dynamic of the family? Pros and cons? Anyone experience more negatives than positives with it? Thanks!