I am married, I have 4 children prior to my marriage, 2 are still home. If something happens to me, how do I make sure my children remain with my husband?

If those are your wishes you MUST make them clear in your will.

Your husband needs to adopt the children if the bio father allows. Unless he is a threat to the child, their bio father will have legal rights to custody of the children at your death ( unless custody and rights to children were lost for some reason)

Write it in a Will!

I will mention while a will is great and should be done, but it really does not matter about what you put in there about the kids. Kids are not property and can not be willed to another person.

The state and custody laws will over rule any will. So unless one parent has lost their rights, that parent ( if alive) will have first rights to their children, After that other family member will have to make application in court.

Your wishes will be looked at, but it is familylaw of the state you live in that makes the difference