Sierra and Sebastian's mom, Brenda Green, spoke to The Dodo about their special relationship. "Sierra is always thinking of games to play with Sebastian and he always seems to go along with them," she said, "Sierra really believes I can talk to Sebastian, so she often asks me to interpret what he is is saying or feeling. She has always been very concerned about him."
Brenda has been recording Sierra and Sebastian's close relationship for years. You can see more videos of the two of them playing together on her YouTube channel.
And you can see the whole adorable hula hoop lesson here.