If I have to put a apostrophe in this sentence would it be like this

The Henderson's never change;They're always complaining about Mr. Scobb farming land that is rightfully their's.

No. There is no apostrophe after names and after their.
The Hendersons never change; they're always complaining about Mr. Scobb farming land that is rightfully theirs.
And they're is not capitalized if you're using semi-colon; you could also use a period here and make them 2 separate sentences.

Further correction:

The Hendersons never change; they're always complaining about Mr. Scobb's farming land that is rightfully theirs.

"Mr. Scobb" needs to be possessive because it is followed by a gerund.
http://grammar.ccc.commnet.edu/grammar/possessives.htm
Scroll down to Possessives & Gerunds.

=)