Does my husband have grounds to include my children from a previous relationship on an application to csa? He has a child from a previous marriage, has no contact but pays csa. The child lives overseas.
We married and I had 2 children already. Their father is deceased. I receive no financial support from his family or in the form if bereaved parent allowance or similar as I was not married to their father.
My husband has taken on my children although not legally adopted them. They have his surname. My husband is the main earner for the family, thus providing for the children. Will these children be considered?

It would help if you would define what "CSA" is. Do you mean Child Support Agency, and he wants to use the financial support he provides for your children as an obligation to help reduce the amount of child support he pays for his own child? What state are you in?

Does my husband have grounds to include my children from a previous relationship on an application to csa?
If it is UK case-then YES.

Not enough information given. In the US, it will depend on the state that the order is paid though.