80 Sibling Announcement Captions (Promoted to Big Brother)

A second-baby announcement is a different post from a first. The first one is about you. The second one is about him — the boy who is about to be a big brother and currently has no idea what that means.

That's where the good captions live: in the gap between how excited he is about the sign he's holding and how little he understands what's coming. Eighty below, short ones first.

Short

1. Promoted to big brother.
2. Party of four.
3. He's getting a roommate.
4. Big brother, incoming.
5. Two under two. Pray for us.
6. One more, spring 2027.
7. He said yes.
8. Adding a small one.
9. Big brother duties commence March.
10. Our best work, again.
11. He has no notes.
12. Round two.
13. Plus one.
14. Growing by one.
15. He's been told. He's thrilled.

Funny

16. He thinks this is going to be great.
17. Currently accepting applications for a roommate. His words, not ours.
18. Only child, expiring March 2027.
19. He agreed to this without reading the terms.
20. We asked if he wanted a brother or sister. He said "a dog."
21. He is expecting a friend who can immediately play trains. We have not corrected him.
22. Big brother, effective spring. He has not been consulted on the start date.
23. Told him there's a baby in mommy's tummy. He asked how it got in. We're moving on.
24. He's very excited about the baby and completely uninterested in the details.
25. Two kids. We are aware of what we've done.
26. He has already assigned the baby a favorite dinosaur.
27. New sibling loading. He will not be sharing the good cup.
28. He is under the impression the baby arrives fully able to run.
29. Our firstborn has been informed and immediately asked for a snack.
30. Existing child unaware of the scale of this.

Sweet

31. He's going to be so good at this.
32. The best thing we ever did, doubled.
33. He made us parents. Now he makes us a family of four.
34. Watching him meet this baby is the thing I'm most looking forward to.
35. He doesn't know it yet, but he's getting his best friend.
36. One more heart to fill this house.
37. He kissed the scan picture without being asked.
38. Everything I hoped for, arriving again in spring.
39. He is going to be the kind of big brother who checks.
40. Our little one is getting a little one.
41. The last few months of him being the only one.
42. He asked to hold the photo the whole way home.
43. Big brother in spring. Small boy for now.
44. Two of you. I can't quite picture it and I can't wait.
45. He has so much love in him and now somewhere to put it.

For the photo with the sign

46. He picked the sign. He also picked the shirt. And the hat.
47. Twelve attempts. He looked at the camera in one.
48. Held the sign upside down for the first nine photos.
49. He can't read it and he's proud of it anyway.
50. This took four adults and a snack.
51. The one where he's actually looking. Framing it.
52. He wanted to hold it himself. Obviously.
53. Sign made by him. Spelling entirely his own.
54. Blurry, because he was jumping.
55. Best photo we've ever taken and he's mid-blink.

Naming the date

56. Arriving March 2027.
57. He'll be two and a half and completely unprepared.
58. Big brother, spring.
59. Two under two, arriving February.
60. He gets a sibling before he gets a full night's sleep.
61. Due in April. He's due a shock.
62. Summer baby, and a very surprised toddler.
63. Counting down, one of us more accurately than the other.
64. Baby number two, fall.
65. October. He'll be three and in charge.

For the parents

66. We did the hard part twice on purpose.
67. Outnumbered as of spring.
68. Two kids and one pair of hands. Should be fine.
69. Our house is about to get significantly louder.
70. Half as much sleep. Twice as much of the good part.
71. Doing it all again, knowingly this time.
72. Second baby, second-hand everything, same amount of love.
73. Slightly less terrified than last time.
74. We know what we're in for. We're doing it anyway.
75. Family of four, spring.

The quiet ones

76. He'll never remember being an only child.
77. This is the last summer it's just him.
78. Same house, one more person in it.
79. He's about to become someone's whole world.
80. Two boys. That's the post.

Worth doing

Take one photo of him alone on the day you announce it. Not with the sign — just him, on an ordinary afternoon, as the only one. It's the last stretch of something and you won't think to photograph it otherwise.

More captions: pregnancy announcement captions for the first one, baby milestone captions, and baby boy quotes.

Preparing him for it? big brother gift ideas covers the hospital gift and the first weeks home.