NDA that I shouldn't join client company for 1 year. Can it prevent me joining sister company of client company?

If I have completed 90 days of notice period completely can a employer deny me relieving letter and F&F seeing I have joined a sister company of the client company?
I have a clause in the NDA that I shouldn't join client company for 1 year. Can it prevent me joining sister company of client company?

Legally, nothing should prevent your movement. But it depends on the policies of relieving firm & joining firm. If your relieving co. in know of things about joining a client's associate, they might create problems. Watch out.