nous sommes brossé

Michael, 

you haven’t included the full phrase, but this usually comes up in relation to phrases similar to  ‘ nous nous sommes brossé les dents (les cheveux). 

Regardless, the past participle is correct - it does not take any agreement as there is a direct object following the reflexive verb - les dents (les cheveux). 

Below cut from a response further down the QandA on this question site. There are also other responses to similar questions in the forum. 

“

          ‘ Nous nous sommes brossé les cheveux ‘ is correct.

The direct object of se brosser in the sentence is ‘ les cheveux ‘ which follows the verb and therefore there is no agreement of the past participle. Agreement occurs when the direct object precedes the verb, which is most often the case with reflexive verbs, but not always - se brosser being one of the exceptions.

This question has come up often and it has been acknowledged the lesson needs a review to address this confusion. Until that is done, try the link below to Laura Lawless site for further explanation. 

https://www.lawlessfrench.com/grammar/agreement-with-pronominal-verbs/ “