Thinking of getting a second bird

Hi! We have a 2 yr old female sun conure who is extremely possessive of me. She likes my finace too but she really loves me. He would like to get a male baby sun conure(6-9 months) as well so he can have a bird himself...we also thought that maybe a "friend" would help our other conure not be such an "attention whore" if you will.

I'm a wildlife biologist and my concern with knowing animal behavior as I do, is that our current conure might attack the new one and potentially kill him due to territoriality and possessiveness over me. We would obviously introduce them slowly but its still a huge concern of mine. I'm also wondering about breeding between the two of them...our current female has been going through huge hormonal changes and showing alot of aggression lately...esp to strangers. My fiance isn't a scientist so he doesn't think of these things like I do. I'll continue to do my research but any info would be greatly appreciated! Thanks!!