Naked Tenant Issue in Texas

[Gabriel H.]

I have a unit in a duplex (in Texas) that's occupied by long term tenants that were there when I purchased the property.  They are an elderly couple and the husband is handicapped.  He can walk with a walker, but it's definitely hard for him to move around.

My sister manages my properties for me since I don't live in the area.  He's a pretty needy tenant and calls her about little issues, and sometimes calls just to chat.  She's been over to his place three times when he's been naked, covered by a thin sheet, and he tells her that he's naked under the sheet.  My sister told his wife that she was uncomfortable the situation, and the wife laughed it off and called him "silly".

Otherwise they're pretty good tenants.  They pay early every month and keep their place in decent shape.

Is there anything we can do to insist that he's clothed when she goes over there?  Can I tell her to tell them "I will not come in your property unless you're fully clothed.", even if they have a service request?  

Looking forward to some creative and maybe even some funny suggestions!  

Gabe