The Cleveland Show Season 1 Episode 21 (The Cleveland Show s01e21) with title “You’re the Best Man, Cleveland Brown!” airs on Sunday, May 23rd 2010 at08:30 pm via FOX.
Here is summary for The Cleveland Show Season 1 Episode 21 :

Much to his dismay, Cleveland finds out that Cleveland Jr. will inherit all of his ex-wife’s belongings and that his parents, Cookie and Freight Train, plan to remarry. To add insult to injury, Freight Train dumps Cleveland as his best man in favor of Donna’s ex-husband, Robert.

Few hours after original series aired on TV, online streaming video for The Cleveland Show Season 1 Episode 21 usually available on Net and of course, if video available, as soon as possible will show you where you can watch this episode for free.