Shared Soul

Unlike other sorcerers your power comes not from your bloodline, but from your very soul.  It may have been due to wild magic, possession, birth or some kind of magical means, but somehow your soul has become fused with that of another.

Mental Fortitude

While you are in control now, the shared soul often challenges you for dominance, as such you've built up a strong mental fortitude granting you resistance to psychic damage.

Self Preservation

The soul you are bound to has its own sense of self preservation, and as such wants to keep its host safe.  When you take a long rest, roll 1d4 and add this value to your passive perception.  The bonus ends when you next take a long rest.

Synchronicity

Starting at 6th level, the shard soul has begun to submit to you, and as such you have gained more control over its power.  Once per short rest you are able to use the twinned metamagic without expending sorcery points.

Superior Synchronicity

At 14th level, you gain the ability to concentrate on two spells at once.  Maintaining the second spell takes up your bonus action.

The maximum level of the secondary spell is 3, and the maximum combined spell level of the two concentrated spells is equal to your maximum spell level -1.

e.g. if you have access to 9th level spells, you could maintain a lvl5 spell and a lvl3 spell, but not two lvl4 spells, and not a lvl3 and a lvl6.

Activating the second spell costs a standard action.  To successfully cast the second spell you must pass a Con check of DC10+combined spell level.  If you fail the check the second spell fails to activate, but the casting slot and your action are both still expended.

When you roll a concentration check to maintain concentration on two spells at once, you do so with disadvantage.  If you fail this concentration check you lose concentration on both spells.

You can use this ability once per long rest, 

Merged Soul

Beginning at 18th level, your souls have finally merged, giving you full control over your previous abilities.

Previous abiltlies are replaced with the following

Self Preservation:  Add your CHA mod to passive perception checks.
Synchronicity (14) You gain advantage on the second concentration spells activation check.