Do both your kids have a game or craft they like to enjoy together? Get them involved and they’ll hardly notice that you’re snapping away the whole time. All you need is a camera that lets you capture your kids without getting right in their faces.
Older siblings love to show off how much they know to younger brothers and sisters, which makes this a good time to take photos, particularly since they are usually sitting close together. Have your eldest ready a story or show the young one(s) how to do something and keep your camera handy. For younger siblings, painting or playing with blocks can offer a colorful scene to add interest to photos.
Snuggled up on a chair together with a comfy blanket and a bowl of popcorn makes for a great photo, so pop in a movie (does anyone pop in movies anymore?) and position yourself to the side of the screen to get some great sibling photos. You may need to leave a few lamps on to ensure you have enough light for crisp photos, or experiment with slightly longer shutter speeds.
Siblings don’t get along all of the time, or even most of the time, so your images shouldn’t just reflect those few perfect moments that you manage to capture on camera. Look for fights, arguments, disagreements, or just plain disliking so your kids can look back on the photos later and see what they were “really” like together. Also, they’re great photos for when your little ones get married!
There are many times where your kids are going to give you awesome expressions, and as a parent, you can probably tell what those are going to be: Christmas morning, on vacation, new puppy/kitten, new bike, playing in the sprinkler, etc. Get your camera out and put it on continuous shooting mode to ensure you capture their happy faces during these iconic times to photograph siblings!
It’s okay to get some posed shots as well, assuming you can get your kids to cooperate long enough. After all, you don’t want all of the child portraits to be candid shots with messy faces or blurring arms. Just try to be reasonable and keep it fun so your kids don’t run away the next time you get your camera out. If you are still having difficulty getting “the” portrait image of your kids, consider having a professional photography session once a year or so to ensure that you have lasting memories of your children and clean and well-behaved kids!