Second marriage and living with step son who is 26 years old?

Terrible! I agree with you. First, sit down and tell your husband everything that is going on and what you dont like, maybe he really doesnt know. Next, the 2 of you, approach the son in a calm civilized way. If he is agreeable, and respects your house and stops all the women visitors, let him stay - if not send him out of the house. If the Dad is agreeable to this, if not then You got to decide!