I asked my little sister to be my maid of honor in our parents’ kitchen, over the same chipped blue bowl we fought over as kids. No speech. I slid a small box across the counter and pretended to check my phone while she opened it. She got to the card and went quiet, and then she swatted my arm, which is how she cries.
Here is the thing about doing this for a sister instead of a friend. You already have twenty years of material. The dumb nicknames, the road trip where the car broke down outside Lebanon, Ohio, the fact that she still owes you eleven dollars from a concert in high school. The box almost writes itself, you just need printables that do not look like you grabbed them off the first page that loaded.
These are the ones I printed, taped to my fridge for a day, and actually put in her box. A couple printed clean at home. A couple I took to the copy shop on Marsh Street because my home printer streaks anything with a deep color. A few links below are affiliate links, so if you grab one it tosses a little something my way. Costs you nothing.
Some links below are affiliate links. If you download one for your day, I earn a tiny bit and it changes nothing on your end.
The card that did the actual crying

This was the one in the bottom of the box, the one I made her dig for. A floral varsity-letter design with a rose, which sounds fussy but read sweet once it was on real paper. I wrote her name across the top by hand and let the printed part carry the rest.
I ran a test page on plain copy paper first and held it across the room, squinting, like I do with everything. Read fine from the couch. Then I printed the keeper on 80lb cardstock and it sat heavy in the hand, which mattered, because she turned it over twice before she said anything.
My one gripe. The floral border runs close to the edge, and my home printer ate about two millimeters off the right side on the first go. I nudged the margins in before the real print. One wasted sheet, lesson learned, fine.
Because mom was getting a box too, honestly

I will be straight, this one was not for my sister. It snuck into the project because I was already at the copy shop and my mother was hovering by the door asking if she got anything. A Mother of the Bride print, clean type, the kind you can frame later without it looking like a receipt.
I printed it on the same cardstock run as my sister’s card to save a trip. Tucked it into a flat envelope, wrote the date on the back in pencil so she would have it years out.
The lettering ships a little light. In my parents’ dim hallway it almost vanished, so I bumped the weight up a notch before the second pass. Took me one squint from across the kitchen to catch it.
The backup I liked more than the first

I almost did not download this second Mother of the Bride one. Then I printed both side by side on the kitchen table and this was the one my sister pointed at, so it went in. Funny how that works. The spacing on this version sat easier, less crowded near the bottom.
I did a plain-paper test, taped it next to the other, lived with both for an afternoon. By dinner it was obvious. This one held up under the overhead light, the other washed out.
Watch the file size on the print dialog. It wanted to scale up and clip the top line of text, and I did not catch it until a page came out with the M half-gone. Set it to actual size and it behaved.
For his side, so nobody felt left out

His mother is the type who notices, so this Mother of the Groom print went in the same batch out of pure self-preservation. I am glad it did. It matched the bride versions closely enough that the three of them lined up on the gift table looked like a set, which was an accident.
I printed it the Tuesday before our shower because that was the only night the copy shop on Marsh Street had the good paper in stock. Slid it in a card sleeve so it would not bend in my bag on the drive.
The font is a touch thin for a darker print, same note as the others. I thickened it one step. If your venue or her hallway runs dim, do that first or you will reprint.
The inside joke I almost talked myself out of

Okay, this one is the inside joke, and I went back and forth on it. Bride’s Drinking Team. My sister and I have a running thing about a very bad batch of homemade margaritas from a camping trip near Hocking Hills, so I printed a couple of these on sticker paper and slapped them on two little flasks for the box.
Printing on sticker stock is its own animal. The ink sat wet longer than I expected and I smudged the first one with my thumb like an amateur. Let it dry a full ten minutes before you peel.
The design itself prints bold and clean, no notes there. Just do not size it down too far or the smaller text turns to mush on a curved surface. Mine wrapped a flask fine at full scale, barely.
A peek at what she was signing up for

This one was a little gift inside the gift. A Welcome to Our Wedding print I folded small and tucked under the card so she could picture the day she was about to help me survive. Felt right to give her a glimpse before the chaos started.
I printed a test at home, hated the gray it came out in, then took the real one to the copy shop where the color actually pops. Came back deep and warm instead of muddy.
The layout has a lot of open space, which I liked, but it means any smudge or fingerprint shows. Handle it by the edges. I learned that after leaving a thumbprint right in the middle of my first decent copy.
The one she gets to open in a year

Last thing in the box, sealed in a little envelope marked do not open. A Happy Wedding Anniversary print, the idea being she stashes it and pulls it out for me and my husband next year. She is the sentimental one of us, so this was bait and she took it.
I printed it on the lightest cardstock of the bunch since it needed to slide flat into a sealed envelope without bulging. Wrote our wedding date on the front so future-her would not forget the assignment.
The only snag was the date area. There is a spot for the year and the printed line under it sat too low, so my handwriting bumped into it. I shrunk my text and it fit. Tiny thing, but it bugged me until I fixed it.
What People Keep Asking
What do you put in a sister’s MOH box?
Honestly? Whatever proves you have known her since she was in pigtails. I put in a printed card, two flasks with a dumb sticker about a margarita disaster, a bag of the exact gummy candy she used to steal from my room, and a sealed anniversary note for her to open in a year.
The candy did as much work as anything I printed. Skip the generic spa-set stuff. Pull from your actual history, that is the whole advantage of it being your sister.
How do I make it personal?
I leaned on stuff only the two of us would get. A nickname on the card, a sticker about a trip that went sideways, a note referencing eleven dollars she still owes me. None of that means anything to a stranger, which is the point.
A friend asked me this once and I told her to write down five things she would never have to explain to her sister, then build around two of them. Worked for me. The printables just gave it a frame so it did not look like a pile of stuff in a box.
Is a box overkill for a sister?
I worried about this. We are not a flowers-and-grand-gestures family, so I almost just texted her. Glad I did not. She still has the card stuck to her fridge.
A box is not too much if it sounds like you. Mine was small, half the contents were jokes, and it cost me maybe thirty dollars including the printing on Marsh Street. The size of it matters way less than whether she can tell you actually made it.
Before You Print a Stack
My sister kept the box. The actual box, the cardboard one I drew a lopsided heart on with a Sharpie because I ran out of nice paper. It sits on her dresser now with the candy long gone and the anniversary note still sealed, waiting.
That is what these printables are for, really. Not the box, the thing she pulls out in twenty years and remembers the chipped blue bowl. Print a test page first, squint at it from the couch, fix the one thing that bugs you, then put it in her hands and pretend to check your phone.