when i was in therapy, i asked my husband, with my Ts consent, if he could start coming along to my sessions for both support and so i could have an extra pair of ears to help me process the sessions. i was easily triggered in sessions due to my CPTSD and would dissociate often. due to the dissociation, i easily could misinterpret things my T was saying or i struggled to even remember what happened in the sessions. my husband attended almost every session (twice a week for a while) for the last 2.5 years of my therapy. because of him being there, i made good progress. since he was there, he knew what i was dealing with in my sessions and could offer better support in between sessions. he also was good at providing info to my T of things that had been happening between sessions (due to the dissociation, i often could not remember or i would down play my symptoms) and he was also a great advocate and witness for me when T was not understanding something i could be trying to convey to him.
for me, having my husband partake in my sessions was a very positive experience that actually strengthened our relationship in the end