Just out of interest.......
For some unknown genetic reason a cross between a tiger and a lion, called a liger, grows a lot bigger than either of its parents.
Have a look at what is probably the biggest cat in the world.
yes.. It is not unusual for hybrids to grow bigger and faster than their parents, it is a phenomenom known as 'hybrid vigor' sometimes the opposite occurs. Look it up on wiki lik below
.http://en.wikipedia.org/wiki/Heterosis