So, I recently got a green cheek conure, and now have also let out 4 parakeets from quarantine. My conure--Kikki--seems to be in love with a particular parakeet. Preening her, cuddling her... and is now attempting to stand on her which I believe is an attempt to mate with her.
There's no way they could ever breed so I wouldn't worry too much about it...as long as there is no aggression from the conure towards any of them, no big deal. If the budgie seems attached as well there's no real harm.