French language Q&A Forum

Is it optional to use the subject pronoun after "mon pére et moi" as in The fireworks example?

Ma sœur et moi nous avons rejoint ... 

compared "mon père et moi avons décidé" in Fishing with Dad?

I understand that this is an idiomatic phrases that means "I know something about ..."  Just curious.  How do the reflexive "me" and the preposition "y" refer to or mean?  "I am familiar with myself" and "at ... in that area"?  The "y" seems redundant since you say "en moteurs" at the end.  Why not, "je me connais en moteurs."

(I'm afraid I can't remember the French question, but this was how I read it in English.)Why is this in the subjunctive? It seems to me to be a fact that the obligation is not needed. Thanks for the explanation.