Unacceptable. As much as a blended family is a family nonetheless, you may have to fall back on the argument that these are your kids, and when it comes to some big ticket items, you’re going to have the final say.
I would ask, however, whether you object because you want to raise them according to your religion. I understand if you don’t agree with me on the following, but I feel like that’s just as inappropriate as relating to the children (note – he’s in a worse position because he is imposing it on the children and you).
So…is it a religious conflict situation, or a situation where you’re not raising them a particular way, and he is attempting to force his position in….