That's an interesting issue. It sounds like it may be your internet viewing is not configured properly or need to set up a port forward through your router. We can fix this simply by going to setup.slingbox.com and selecting set up Internet viewing. If your Internet viewing or port forward is already set up completely then it could be the Internet speed on your cousin's end in Spain. I would recommend taking a look at the link below about port forwarding and Internet speed:
I hope this is helpful!
The Sling Moderation Team