The most important reaction to Othello and Desdemona’s marriage is that of her father, Brabantio, who is initially vehemently opposed to it. The opinions of the rulers of Venice are also important, as they could act to annul the marriage; if coerced, they could also punish Othello. Once they hear from Desdemona, they endorse the marriage.
When Brabantio intrudes on a military strategy meeting of the Duke of Venice and the Senators, he is so upset that the Duke at first assumes that Desdemona is dead (Act I, Scene 3). Brabantio tells the Duke, no, but
She is abused, stol'n from me, and corrupted
By spells and medicines bought of mountebanks;
For nature so preposterously to err,
Being not deficient, blind, or lame of sense,
Sans witchcraft could not.
The Duke replies that the full weight of the law will be brought against the offender, whom Brabantio then names as “the Moor.”
The First Senator then asks Othello what happened, showing that he does not take Brabantio’s claim at face value.
Did you by indirect and forced courses
Subdue and poison this young maid's affections?
Or came it by request and such fair question
As soul to soul affordeth?
When Desdemona comes in and speaks with love of "consecrating her soul to him," the Duke is persuaded and encourages her father to allow “these lovers Into your favour.”
Although Brabantio then accepts that their union was voluntary, his opinion of his daughter is diminished, and he advises Othello that she might deceive him as she had deceived her father.