Realistically you might hit your guy but how much fun is that?
Not just an ally, an enemy can act as a meatshield for their buddy by just standing in your way too.Not by default. Though, if your ally is between you and your target (which is likely in a melee), the target will have half cover from you.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.