The main question is: how reliable do you want it to be?
The unreliable option
A 9th-level sorcerer has enough sorcery points to twin a spell scroll of foresight; however, spell scrolls have the following restriction:
If the spell is on your class's spell list, you can read the scroll and cast its spell without providing any material components. Otherwise, the scroll is unintelligible.
Therefore, the lowest level option is Sorcerer 9 / [Bard, Druid, Warlock, or Wizard] 1. Unfortunately, a 1st-level bard, druid, warlock, or wizard can only cast 1st-level spells normally, so the following restriction applies when using the scroll:
If the spell is on your class's spell list but of a higher level than you can normally cast, you must make an ability check using your spellcasting ability to determine whether you cast it successfully. The DC equals 10 + the spell's level. On a failed check, the spell disappears from the scroll with no other effect.
If the sorcerer has 20 Charisma (and chose bard or warlock as their single additional level), they only have a 30% chance of successfully casting the spell.
The reliable option
We need 9 levels of sorcerer to be able to twin foresight, as well as 17 levels of bard, druid, warlock, or wizard to avoid the spell scroll ability check. Since that is impossible, we need another option. The 8th-level spell glibness holds the key:
Until the spell ends, when you make a Charisma check, you can replace the number you roll with a 15.
The spellcasting ability check will be Charisma-based, if we choose a level of bard or warlock. With glibness and at least 18 Charisma, the spell scroll ability check cannot be failed (15 + 4 = 19).
But wait! Glibness isn't a sorcerer spell. Fortunately, we can use wish to duplicate glibness. Putting all of that together, we'll need Sorcerer 17 / [Bard or Warlock] 1.
The mount option
The spell find steed has an interesting clause that gives us another option (which works for find greater steed, as well):
While mounted on your steed, you can make any spell you cast that targets only you also target your steed.
Therefore, if you cast foresight while mounted, your steed also receives the benefits of the spell. Find steed and find greater steed are paladin-only, but a bard can use Magical Secrets to grab one of them. Bard 17 can get you foresight and find greater steed without much fuss. Wizard 17 could use wish to duplicate find greater steed, take a long rest, and then use foresight while mounted for the same effect.
The "cheating" option
This isn't technically what you asked for, but I'm including it for the sake of completeness. Wizard 17 could use simulacrum to create a copy of themselves, then the wizard and their sim could both cast foresight. Bard 17 could do the same, if they took simulacrum with their Magical Secrets.