Maternity photos without step children

I am in my second trimester and am looking to book my shoot for this summer as I am due at the end of August. However I do not want maternity photos with my stepson because this is my first. I would love family photos with him after baby is born but I want my maternity photos to be special to baby and I. Is this unreasonable? I adore my stepson but my husband makes it very clear to him that I am not taking his mom’s place and I never try to be his mother. This is why and where I would feel weird if he were in my maternity photos.