I just started a game setting out as a bloodrager with the copper dragon bloodline, But when i reach lvl 6 and took a lvl in Dragon disciple, suddenly i had 2 bloodlines, 1 from bloodrager and 1 from sorcerer
a few lvls later i realized both bloodline were progressing, so at lvl 8, Bloodrager 5, Dragon disciple 3, i had my bloodrager bloodline at lvl 8 and the sorcerer were at lvl 3

This can't be intentional, but is it a bit broken?

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This is the 'Pathfinder: Wrath of the Righteous' forum you are posting in, so...

Necromancer here,

According to a ruling from piazo it might be possible for Bloodrager to count as a sorcerer in regards to bloodline powers. This means the Dragon Disicple class Levels count as Bloodrager class levels for Bloodline powers.

Quoting the SRD:

'Blood of Dragons

A dragon disciple adds his level to his sorcerer levels when determining the powers gained from his bloodline. If the dragon disciple does not have levels of sorcerer, he instead gains bloodline powers of the draconic bloodline, using his dragon disciple level as his sorcerer level to determine the bonuses gained. He must choose a dragon type upon gaining his first level in this class and that type must be the same as his sorcerer type. This ability does not grant bonus spells to a sorcerer unless he possesses spell slots of an appropriate level. Such bonus spells are automatically granted if the sorcerer gains spell slots of the spell’s level.

( According to Paizo, Bloodragers can be Considered Sorcerer When it Relates to this Prestige Class due to it being released after the Prestige Class did. So it would add to Bloodragers Bloodline)'

The last sentence was added as a comment but I guess it means that due to the Bloodrager class being released after the dragon disciple, the Dragon Disciple's abilities got an errate that would allow its ability's to stack with that of the Bloodrager.

So the stacking was not planned initially; only after the Bloodrager got released.

So all Sorcerers = 10 Sorcerer + 10 Dragon Disciple ? Cause ability bonuses and wings ? Do spells progress normally under Dragon Disciple ?
What is the best class mix for a mage to cast as sorcerer but learn from scrolls ?

Dragon Disciple adds all his Sorcerer Class Levels in order to calculate which bloodline powers he gets.

Spell progression is a bit slower; sorcerer 10 + Dragon Disciple 10 leaves with with a Caster Level of 17 (DD only has CL+7 at level 10)

Do you mean the magus class or mage as in second edition generalist wizard?

I mean what class should I choose to have those options, Magus ?
Cast any spell I want without memorizing it specifically like Sorcerer, but learn new additional spells from scrolls like a Wizard.

Maybe try Arcanist? Arcanists learn and prepare spells like a Wizard, but cast them like a Sorcerer. You do need to select which spells you want to have available for the day before you rest, but you don't need to allocate spells to specific slots, so if, say, you have Magic Missile and Sleep prepared, you can spend all your casting slots on Magic Missile if you happen not to encounter any enemy that's vulnerable to Sleep. But, if you know that Sleep will be useless, you could put a different spell in that slot before you rest.

Thanks, sounds better than wizard, I think I'll try Arcanist, but what do you think about Wizard 1 Sorcerer 19 ?

Only if you can find a Wizard subclass that gets a bonus at level 1 that's worth giving up a caster level, and it usually isn't worth giving up one.

(Note that you won't be able to learn a spell above 1st level from a scroll and actually cast it with the Wizard 1 Sorcerer 19 build.)