Frolicking Squirrels

I heard quite a bit of chittering up high in the trees. What I saw made me laugh. There were multiple Eastern Gray Squirrels (I think I counted six of them) frolicking from branch to branch, running up and down the stems and chasing each other here and there. Enjoy this short video of their antics. Might they all be siblings? I know that the average litter is between 1 to 4 young with a maximum litter size of 8.