So Basically A and B were a couple and they broke up or one of them died.Then A and B's sibiling start to have feelings for each other
Example:Devil-In-Law: A dies then A's sister and B start having feelings for each other.
Example 2:A Love To Kill: B and A have broken up and then B's Brother falls for A and A falls for B's brother.

No BL
Historical is fine

Romance in The Rain between a half-sister and the other sister's prospect husband (let's say they're going to get married-even if they're not dating-if the first sister doesn't snatch him).

Love Scar between a new wife with her brother-in-law who's her ex.

Love Keeps Going between an ex-girlfriend and the ex's younger brother.

Bread, Love, and Dreams between a 'half-brother' and an ex-crush or ex-girlfriend (they're not actual brothers apparently).

Moon Lover Scarlet Heart Ryeo between 8th prince's ex-kinda-dating and 4th prince.

If it include fake relationship then:

My Cherie Amour between a younger brother's fake girlfriend (but the younger brother's feeling is real) and the older brother.

Wedding Impossible between the older brother's prospect wife (marriage contract) and the younger brother.

 autumn iris:

Romance in The Rain between a half-sister and the other sister's prospect husband (let's say they're going to get married-even if they're not dating-if the first sister doesn't snatch him).

Love Scar between a new wife with her brother-in-law who's her ex.

Love Keeps Going between an ex-girlfriend and the ex's younger brother.

Bread, Love, and Dreams between a 'half-brother' and an ex-crush or ex-girlfriend (they're not actual brothers apparently).

Moon Lover Scarlet Heart Ryeo between 8th prince's ex-kinda-dating and 4th prince.

If it include fake relationship then:

My Cherie Amour between a younger brother's fake girlfriend (but the younger brother's feeling is real) and the older brother.

Wedding Impossible between the older brother's prospect wife (marriage contract) and the younger brother.

thanks a lot