The parents of the groom usually speak second in reply to the parents of the bride, based on the traditional wedding protocols in which the bride has precedence over the groom.
This protocol varies, and if one parent doesn't want to speak, for whatever reason, the speeches should be scheduled and a time allotted for their speeches. The parents are the senior speakers, and precede all other speeches.
Speeches don't actually have to be of equal length, but equal time should be allotted on principle to parents.
Note: Speeches are timed at 120 words per minute. This is a useful measure to ensure everyone gets to speak and that speeches don't take up too much time at the wedding reception.