"Katie ...," she complained.

"Fuck her 'til she cums," Katie ordered.

I looked into my sister's eyes again and found her looking back.

"Please ...," she said quietly.

"Please do it - or please stop?" I asked.

"Please make me cum on your cock, little brother," she said.

"Little!" Katie snorted.

My sister shot her a quick smile and then looked back at me and nodded.

I slid my slick prick in and out of my sister's twat - loving how tight she was - and thankful that my penis was already well coated in Katie's and my fluids.

Katie's lips found Julie's but my sister's eyes stayed locked onto...