I ask this as an only child. This has happened a couple of times now and one of those times was yesterday afternoon: Both of them decided to boycott their afternoon naps. You might think that they heard each other in their rooms and decided that they would rather play together. But, no, this is not the answer because I keep a fan on in Madelyn's room and Pierce has a noisemaker. Both do a very good job of drowning out noise.
Madelyn's normal routine on school days is that she comes right in and we go straight into her naptime ritual (potty, read, pray, sing song). Then she goes to sleep/stays in her room for about 3 hours. I had to go into her room several times yesterday to ask her to calm down, read silently (she can't really read, but you know...), and stop singing. She finally crashed at 4:00, which isn't great because I had to wake her up soon after that just so she would go to bed last night.
Around 2:30, Pierce went into his whiny spell, which usually means "Naptime, please." For whatever reason, he did NOT want to sleep. So, after about 20 minutes of really fussing, I got him up. Thirty minutes later he went into his whiny spell again, so I took him back to his bed. He might have slept for 30 minutes.
This made for the longest afternoon/evening in my nearly three years of motherhood. I woke Madelyn up at 5:00, and she was soooo upset with me. I really don't think she said a word to me all evening that wasn't in a whiny, nasaly pitch. Meanwhile, all Pierce did all evening was cry and whimper. They both wanted to be held all evening. Now, they both went to bed at 7:00, and I did not hear a peep out of either of them until almost 8:00 this morning. That was very nice, but the afternoon it took to get that 13 hours of peace was not worth it.