I have been with my SO for 6 years now and I have 2 children  from my prior marriage and he has 1 from his prior. We recently got married and my children live with us and he gets his son every other wknd. We went food shopping and when we had to pay he suggested we split in 3 (Him, My Ex bc of my children and Myself) I was so bothered by that bc I would never do such a thing. What do you think?