I've had a similar thing happen several times in my current game as Ireland, although I didn't marry my current ruler directly into other titles. Out of 5 kids my heir has a claim on England from his mother (which I intend to use as soon as my current ruler dies), my second son married the Queen of Aquitane on her 16th birthday and his son will inherit the whole kingdom (which is quite healthy at the moment, with the ruler owning 8 counties and almost all the counties of the kingdom in its influence), my first daughter got a matrilineal marriage with the heir of the king of Castille/Galicia/Leon and her son will be king once the current king and his son dies off, my second daughter got a matrilineal marriage with the heir of Norway (although due to inheritance laws their son won't be taking over, although I may call him back to my court and enforce his claim when his father dies), and my third daughter got a matrilineal marriage with the third heir of France (and my assassins took care of the guys in his way, heh heh).
I'm still playing my first generation char, so these are 2nd gen characters. The third generation of the family will be in control of a big chunk of Spain, Aquitane, and France without any intervention. My heir will inherit the crowns of Ireland and Wales and should be able to mop up the fractured England pretty easily within a few years, since it has kinda broken down into small duchies and counties with the king only controlling about 1/4 of it. And once that's done, with my heir's help his nephew will be able to take the Norwegian crown (and possibly pass it back to my heir if I'm feeling cruel enough to assassinate the nephew).