I came upon this interesting thought of Cersei's in A Feast for crows in the second Cersei chapter
(during Tywin's Funeral)
Cersei looks at Margaery and thinks:
Queen Margaery, she reminded herself; Joff’s widow and Tommen’s wife-to-be. Margaery looked very like her brother, the Knight of Flowers. The queen wondered if they had other things in common. -A Song of Ice and Fire: A Feast for Crows, Cersei.
I am specifically interested in the line where Cersei wonders if they have more in common:
Does she mean what Margaery and Loras have in common with each-other, or Margaery and Loras have in common with Cersei and Jaime?
Is Cersei wondering if Margaery and Loras are
also sleeping with each-other as Cersei and Jaime are?
Or is she wondering whether there are things about Margaery (character wise or in looks) which Loras shares?