It is not like Loki wants to use their mother against Thor, but his stubborn older brother just keeps pressing the matter. Thor may notice the flinch in Loki's posture when he steps forward and a failed attempt to step back when he makes a grab for the younger brother. Loki expects worse than being let go again, but...

...but of course Thor remains weak.

He makes a show out of not being too bothered by that reaction. His actual brother, he is almost certain, would not hesitate to severely hurt him in this situation. If he knew. If only he knew.

"Why would I tell you." he snarls back and it is not a question.