Oh so the mother is also the daughters real mother, so they are his half sisters.Well, the mother is his real mother in the version here. Not sure if it would work story wise when the sisters become his real sisters so they will probably stay his half sisters.
I somehow assumed that they are his step sisters. Probably just read that they are from another marriage and thought that they are the other husbands daughters.
Thx for clearing that up. I will try it out.