Sounds like typical toddler behavior.
You know, "toddler property laws"...
1. If I like it, it’s mine.
2. If it’s in my hand, it’s mine.
3. If I can take it from you, it’s mine.
4. If I had it a little while ago, it’s mine.
5. If it’s mine, it must never appear to be yours in any way.
6. If I’m doing or building something, all the pieces are mine.
7. If it looks just like mine, it’s mine.
8. If I saw it first, it’s mine.
9. If you are playing with something and you put it down, it automatically becomes mine.
10. If it’s broken, it’s yours.
Honestly what I would do in your situation is ignore.
I would reply ONLY to the child you spoke to or were speaking to and simply ignore the comments and protests from the other. I know it's hard but sometimes ignoring is best. In a toddler's world ANY attention is attention.
Encourage the other child to pay attention to you, continue speaking or whatever they were/are doing verses replying to the other child.
Rinse and repeat probably 2-3 dozen times per day and cross your fingers that either or both of them pick up real quickly that it is not an appropriate way to get attention.
