Im a noob! need help!

Guys if I need a Weapon+ on a hero, do I need to inherit the weapon from a 5* hero? or could it be inherited from a 4* hero and then upgraded?

For example, Brave Bow from a 4* Gordin to my Halloween Jakob, and then upgrade it to Brave Bow+

I'm 95% sure that i need to upgrade the 4* Gordin to 5* and then inherit, but that 5% of uncertainty is stopping my fire emblem addicted fingers.

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