The therapy is about you and and your internal state and your outward orientation changes accordingly.

However many therapists do give homework and do advise changes in your 'real world'.

The first couple of sessions involve your determining if the therapist can help, the therapist determining if they can help you, and the setting of therapeutic goals. None of that is really a unilateral process.

If therapy is for you, Its not something to engage in to change others. If you think you will benefit you shouldn't avoid it because your changing might effect other people, imo.

You will get to define therapeutic goals and desired outcomes, but therapy is a dynamic, fluid situation and nobody knows exactly where it might lead. So I say there are no guarantees that therapy won't effect your other relations.