Et ce qu'ils se sont déclaré était tellement émouvant

Question

In the writing challenge "Les noces d'or de mes grands-parents" the phrase "Et ce qu'ils se sont déclaré était tellement émouvant" appears. Why is there no plural agreement on the verb "déclaré "?

It sees to be the same case as this example in the lesson "Conjugate reflexive verbs (+être) in Le Passé Composé (conversational past)":

Elles se sont disputées = They had an argument.

Is it because the verb has an object which precedes it and the rule of agreement with a prior object takes precedence over the rule of agreement with the subject?

Something like case 3 1/2 here:https://www.lawlessfrench.com/grammar/agreement-with-pronominal-verbs/

Accepted Answer

Hi David,
'Se sont déclaré' has no -s because the object is 'ce que' which is is just neutral and represents 'what' in English .
For instance if it was -
"L'amitié qu'ils se sont déclarée...' 'déclaré' would have to agree with amitié which is feminine and singular...
 
Hope this helps

Answer

I found a detailed explanation in the section "Reflexive verbs with a direct object" on this page: http://www.french-linguistics.co.uk/grammar/past_participle_agreements.shtml.

They say "There are some cases of reflexive verbs where the reflexive pronoun actually represents an indirect object, generally with the sense of "to myself", to himself", "of himself" etc"

So in this case "se" (i.e. ils) is the indirect object here and, as you say, "ce que" is the direct object.

Thank you.