Lady Thimbelby and Viscountess Andover were the daughters of Thomas, Viscount Savage. Elizabeth, standing on the left, married in 1634, while Dorothy wed in 1637.
The messenger angel offers roses to Dorothy, which suggests it is her marriage that is being celebrated. Fittingly, the flowers are an attribute of Saint Dorothy, her namesake. The marriage was a love match, as Dorothy eloped with Charles Howard before she married him.
However much biographical information is read into this image, Van Dyck has produced a complex and animated composition that enlivens traditional portrait conventions of the time.