im wondering since they are in the same egg group and it is dratini's hidden ability
No only a female DW Dratini, Dragonair, Dragonite can pass down Marvel Scale.
Source: Knowledge on DW breeding
No. Abilities cannot be passed between different species.
Abilities can only be inherited from the female parent, and since the female parent determines the species, there is no way of passing an ability to a different species.
Sadly, abilities cannot be passed on like that. Only a female Pokemon with its Hidden Ability can pass it on to its kids. And since the kid is always the specie of its mother, you can't pass on abilities. So even though it could be a convenient way to pass abilities, it doesn't work.
