The Hapsburgs sign a family compact, which arranges for the
Archduke Ferdinand to succeed to the imperial title and the
Hapsburg lands on the death of his brother Charles V, while
Charles's son Philip will then succeed Ferdinand. However, this
agreement was abrogated with Charles V's abdication in 1555, when
his possessions were divided between the two younger men, Ferdinand
taking on the Empire, while the Spanish dominions went to Philip.
Citation:
Editors. "Hapsburgs agree that Archduke Ferdinand will succeed Charles V".
The Literary Encyclopedia. First published 01 November 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=14816, accessed 25 May 2013.]