How to address a mother and son?

My niece just sent her STD's to us. Our adult kids got one addressed to themselves, my husband, myself and two younger children received one addressed to us....

Mr. and Mrs hubby N (last name), and D & A

Ms. Emily Cates

Master Ben Cates

Or whatever his last name is. It's ok to ask.

That would be my guess.

It depends on whether you do inner and outer envelopes or whether you are using one envelope.

With the inner and outer combo, you could address the outer envelope formally to Ms. Emily Cates with her address and then use the inner envelope to indicate both of them are invited. Since they're family, you could informally address them as Aunt Emily and Ben on the inner envelope.

If you're doing outer envelopes only, you could simply ask her if Ben took her last name in the adoption and if she says no, ask for his last name. Usually when you address children by name on an outer envelope, they're listed on a line below the adults. I see no issue with putting them on one line if they will fit, and your example is fine if they do share a last name, but if they don't, you could address them on separate lines:

Ms. Emily Cates

Mr. Ben Last name

Address

JustKidding that is so cute, I love that idea. I might do that for my cousins!

We did Mr. and Mrs. firstname lastname

child firstname

My FSIL has 2 fosters and 1 adoptive we just did "Shumway Family"

For families with children (whether that meant 1 or 5) we just used "The Smith Family" to avoid any confusion.