How to address unmarried couple with children?

Do you know if your aunt plans on taking her fiance's last name? If so, I would address it as "The P Family". If not and their children are young, I would probably address as "Bryan P and Gena L" and then on their RSVP just put that you've reserved 4 seats and they'll know the kids are welcome. Plus like you said, it's close family so I don't think they'd make a fuss

I would just address them by their names. "Jimmy & Lindsey and Family" or even "Jimmy, Lindsey, kid 1, kid 2".

Are all the children in this situation minors? If they're over 18, you can send them their own invitation with just their name on it.

If they're minors, I would address the invites as:

Jimmy LastName, Lindsey LastName & Family

or

Jimmy LastName and Lindsey LastName & Family

Same thing applies to your aunt!

I'm doing mine as Mr Brother Lastname and Ms. Girlfriend lastname and Family. I'm not sure if that is the "appropriate" thing to do but it's what is working for us.

I addressed with the kids names on the bottom line.
“mr. Jimmy Lastname and miss Lindsey lastname
kid 1 first name and kid 2 first name
street
city, state zip”

i also did married couples with minors this way too
“mr and Mrs John smith
jonny, Timmy, and Lucy
street
city, state zip”

I have a few cousins with kids that kept their they names after marriage and addressed their invites like this:

Ms. FirstName LastName, Mr. FirstName LastName, Kid 1 FirstName, and Kid 2 FirstName

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I like the two line idea, I don't know why I didn't think of or consider that lol. Thanks so much!

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I think that's perfect

I did it by two lines:

Mr First name Last name and Ms. First name Last name

Miss child's First name Last name (Can just do first name if you want)

I only used "The ___ family" for married couples with children. I didn't put "and family" on anything because to me leaves too much up to interpretation.

In this situation, I did:

"John Smith & Jane Doe

Johnny, Janie, James"

So addressed each adult with first and last name, added the kids first names only underneath.

I did the following:

Outer envelope:
John Smith and Jane Doe

Inner envelope:
John Smith
Jane Doe
Janet Smith (child)

I wouldn’t write anything to “and family” I’d just list the names of all the people invited (including the kids?

I'll just throw this out there... My mom mailed fiance and me a card when we bought our house. She addressed it

Sara & Nolan
Street
Town state zip

Weeks go by and she asks if we got the card. I told her no. She contacted the post office. They said since it didn't have last names it might not be delivered... Idk if that was just and excuse they used or if it's a real thing. She mailed a new card with last names and we got it right away. Eventually like maybe a month later we got the original card, but it was delayed by a lot.

I think "The ____ Family" wouldn't work since they (presumably) have different last names. I would go with listing the parents on one line and the kids on the next line:
David Smith and Anne Brown
John, Matthew, and Sarah

I think the best way to address them would be, "Mr. Smith, Ms. Jackson & Family"

My cousin isn't married to his daughter's mother, but they all live together. I addressed it "Derek, Serena and Sawyer".