"Yeah your nice big cock looks good in your sister's face?"

Before he could answer I placed my mouth over his cock and started slowly sucking it in and out. I was only going down about halfway and was using my hand on the base jerking him off as I blew him.

"Oh that feels so good sis." Mark whispered as he reached down and ran his fingers through my long black hair.

"It's supposed to." I told him then resumed sucking on him.

With each stroke of my hand I let my mouth go down deeper until I was taking his entire cock down my throat. Mark started twitching...