♪He can cry if he wants to, cry if he wants to, cry if he wants to, be~cause its Brady's Birthday.♪
Anyways, if there's any child character that can be classified as a pure magic user type out of all the 2nd genners (which is no small feat given how many mothers are magically inclined), it would have to be Brady. For starters, his mother Maribelle is tied in having the best Luck and Resistance stat cap modifiers of any gen 1er not referred to as The Avatar and a solid Magic cap as well, but pays for it dearly with the worst possible modifiers for any 1st genner (including The Avatar) in both Strength and Defense. The problem stems from the fact that there really isn't a way to completely fix such massive negatives in such crucial stats with any 1st genner outside of either Stahl (+ inheritance will bring his physical stat cap mods up to 0) or The Avatar with an emphasis on either Strength or Defense and a penalty on either Magic, Speed, or Resistance (one stat will have a +2 in it and the other will be unmodified). Now if Brady had been female, this wouldn't necessarily have been a problem since the female exclusive classes are either magic based or a hybrid, thus expanding his choices, but he's a male and limited to the classes that can be used by either gender. As it is though, his only choices for magic using classes are the Mage, Dark Mage, Priest, Thief (Tricksters can use Staffs), Tactician class trees (and maybe the Myrmidon class tree since it and Swordmaster have higher than average Magic caps, although Brady will probably run off of Levin Swords only which are hard to come by until the end of the postgame chapters) and Dread Fighter (if DLC is an option). And unless Brady is The Avatar's son, the Tactician option is immediately out (and same with Dread Fighter if DLC isn't an option either). On top of that he already defaults in the Priest class and has access to the Mage and Cavalier class trees so the only class trees he's interested in inheriting at all are the Dark Mage and Thief lines. That means that Brady's highest priority for a father will be someone who can pass on those two classes, and it just so happens that Henry is perfect for the job (especially since Henry also sports the second highest 1st genner, non-The Avatar, Magic stat cap modifier, behind Ricken). Seriously, even moreso than Gaius is tailored to Noire, or Donnel is tailored to Kjelle, Henry is the one father who's perfect for Brady. Hell, the only class overlap Henry will have with Brady is in Dark Knight. His alternative options would be Donnel (to maximize his Luck cap modifier for an Armsthrift that needs no Limit Breaker to run perfectly and a Morgan with the single highest chance to activate Miracle in the game, outside of a Chrom sired Morgan with Rightful King), Gaius (for Thief/Myrmidon access and possibly Counter since his damage output is going to suck anyways), and Ricken (to maximize his Magic cap modifier for a Morgan with the absolute highest possible Magic based damage output in the game; and possibly the lowest possible Strength cap modifier if The Avatar takes Strength as her penalty). He can also help you sire a Morgan with the highest possible Resistance cap modifier in the game if Brady's father is Libra (and Brady will at least get Dark Mage out of the deal, so it won't be a total wash), as well as the lowest Defense cap modifier in the game if Brady is sired by either Virion or Lon'qu.
As for skill set up, Brady will hopefully be mothered into the Galeforce, he's guaranteed Tomefaire, Luna, and Aegis, and he can get the all important Aggressor from Dread Fighter (again provided that DLC is an option). With Henry as a father, Brady will have access to Gamble (higher crit rates), Tomebreaker (not particularly useful since fellow magic users will likely have high Resistance), Lucky Seven (for added survivability), Movement +1 (always nice), and Vengeance (stack with Wrath, Miracle, and either Anathema or possibly Counter for comeback hilarity; although the lack of Vantage will make this a one shot wonder).
Basically, Brady IS your goto magic guy for the second gen outside of a Morgan specifically specced to emphasize magic. Of course, this comes with all the usual drawbacks of being a pure mage in the form of being a glass cannon (although the Sorcerer class is no slouch in the Defense department and his growth rate in Defense is higher than his mother's) and being fairly useless against magic users and other high Resistance classes (although Luna will help a lot), but his lopsided nature also makes him a necessary step for building many of the specialized Morgans.