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This mod will make the interaction "Propose.../move in" for all ages. The Teen NPCs and Townies (kids and teens) are included. I made a few tests and work great. The toddlers weren't included. 

Adult to teen = no problem 
teen to adult = no problem 
teen to elder = no problem 
teen to kid = no problem 

I don't tested yet with others types, so if you are interested just download the file. 

This is my first try to make a modification on BHAV things. I don't know if this is 100% stable. I just made the action don't check the Age Test behaviour and enable the pie menu function to childrens and teens. Very simple and basic. 

And another thing: the menu shows when the relationship is at a higher score. 

i'm a brazilian guy... so sorry for the bad english. 

EDITED: Put the file in Downloads folder. Don't forget to backup your Neighborhood before use this mod. It was not fully tested yet but no serious problem was found so far. 

EDITED #2: I didn't change the behaviours of NPCs. The Social Bunny, despite you can interact also, do not have this option. My doubt was if the Social Bunny was considered as a teen or kid for the interactions. So, i edited the description for a better understanding. Only teen NPCs like the clerks and papergirl/boy can move in. Sorry for that. 

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