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Who needs biological sisters anyway?
Despite how cold and formal the whole “sister-in-law” title sounds, those ladies are still family nonetheless. And be that the case, they deserve every bit of love and acknowledgment that our blood relatives get—hey, maybe even a bit more kindness to compensate for the whole “you’re only my sibling through marriage” aspect of it all. To be fair, SIL relationships can definitely vary, and they can range from being your BFF to just another faintly familiar face you see during family gatherings. However, since you’re here, I have to assume that you care enough about her to give her a shoutout on the big D.O.B.
This is why we’re going to provide you with some ridiculously sweet birthday message inspo, because that blank CVS card or text message isn’t gonna write itself. This note should be warm—but not corny! Familiar—but genuine! Thoughtful—but concise! No matter if this is your partner’s sis, or your own sibling’s partner, sending some loving words her way on this special day might just take your bond to the next level. So with those stakes in mind, feel free to steal any of the lovely little messages we’ve got down below. (And tell your girl we said happy birthday!)
Funny birthday messages for your sister-in-law
- Sure, you were [your partner’s name]’s sister first, but we all know who your favorite sibling is now. Happy birthday, sis.
- Happy birthday queen. I’m so grateful that you came with the ring. Hope your day is perfect!
- Shoutout to you, birthday queen. I’m looking forward to the many chaotic family functions that we have ahead.
- Girl, I don’t know how I survived before you came into the picture. Have the best day!
- Happy birthday! You’re the life of the party, and what we lack in childhood memories, we definitely make up for in childish behavior together.
- I’m so glad you and [your sibling’s name] went through all of that wedding hoopla just so that we can legally call each other family. How considerate of you both. :)
- You know what they say, “When life gives you in-laws, you’d better pray that [your sister-in-law’s name] is one of ‘em." Have the best birthday ever!
- The ring? Pricey. The wedding? Pricier. Finally having a sane ally in this family? Truly priceless. Happy birthday sis.
Sweet birthday messages for your sister-in-law
- We may not have been raised together, but it feels like I’ve always known you my whole life. Happy birthday, and thanks for being the best.
- Excited to embark on another beautiful trip around the sun with you! I hope this year is nothing short of perfect.
- They say you can’t choose your family, but I think my [insert sibling] did a solid job of choosing for us. Happy birthday, angel.
- Thank you for being such a light in our lives, I’m so proud to call you family.
- You’re my hero in every sense of the word, and I couldn’t ask for a better sister-in-law. Hope your day’s amazing.
- Our family truly wouldn’t be complete without you. Happy birthday!
- Happy birthday sweetness! You bring the good times and the laughter everywhere you go, and we all love you for it.
Lighthearted birthday messages for your sister-in-law
- Who needs biological sisters anyway? Love you, and have a magical day!
- The years may change but my love for you stays the same! Happy born day, sis!
- I hope this new year brings you even more blessings and success, happy birthday!
- Happy birthday! You deserve all of the joy and praise every day, but especially today.
- My only complaint is that I wish I’d met you even earlier in life. Happy b-day, and thanks for being you.
- As far as in-laws go, you’re truly the GOAT. Love you long time, happy birthday!
- International [your sister-in-law’s name] is one of my favorite holidays every year. I will take any and every chance to celebrate you!
- Happy born day superstar. Being as cool as you is a full-time job and you excel at it with ease.
- May all of your wishes (and then some) be granted this year. Happy birthday.
Annabel Iwegbue
Annabel Iwegbue is an assistant editor at Cosmopolitan where she primarily covers lifestyle and fashion. Before joining Cosmo, she covered entertainment at Harper's Bazaar, The Knockturnal, and Black Film. She's originally from Charleston, South Carolina, and is currently based in Brooklyn, New York. She holds a B.A. in Journalism and Cinema Studies from New York University. You can check out some of Annabel’s work here and also find her on Instagram and Twitter.
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